update telnet server documentation (build procedure modification, add measur command)

 # Please enter the commit message for your changes. Lines starting

common/utils/telnetsrv/DOC/telnetmeasur.md

+measur command can be used to get cpu usage or signal processing statistics from a running eNB instance.
+
+
+Measurments can be displayed by groups, the list of available groups can be retrieved using the `measur show groups` command.
+```bash
+softmodem> measur show groups
+                           name       type 
+00                           enb   ltestats 
+01                        enbues   ltestats 
+02                           rlc   ltestats 
+03                        phycpu   cpustats 
+04                        maccpu   cpustats 
+05                       pdcpcpu   cpustats 
+softmodem>
+```
+By default the oai softmodem doesn't compute cpu usage measurments, a specific command allows to enable them.
+```bash
+softmodem> measur cpustats enable
+softmodem> measur show phycpu
+--------------------------------- cpu (4 GHz) measurements: PHY (cpustats enabled) ---------------------------------
+00                   phy_proc_tx:           40.217 us;             178   | 01                   phy_proc_rx:            0.000 us;               0 |
+02                      rx_prach:           40.123 us;               9   | 03                      ofdm_mod:            0.000 us;               0 |
+04          dlsch_common_and_dci:           39.311 us;             178   | 05             dlsch_ue_specific:            0.878 us;             178 |
+06                dlsch_encoding:            5.667 us;              11   | 07              dlsch_modulation:            5.398 us;              11 |
+08              dlsch_scrambling:            1.398 us;              11   | 09           dlsch_rate_matching:            1.367 us;              11 |
+10        dlsch_turbo_encod_prep:            0.000 us;               0   | 11        dlsch_turbo_encod_segm:            0.000 us;               0 |
+12             dlsch_turbo_encod:            2.408 us;              11   | 13     dlsch_turbo_encod_waiting:            0.000 us;               0 |
+14      dlsch_turbo_encod_signal:            0.000 us;               0   | 15        dlsch_turbo_encod_main:            0.000 us;               0 |
+16     dlsch_turbo_encod_wakeup0:            0.000 us;               0   | 17     dlsch_turbo_encod_wakeup1:            0.000 us;               0 |
+18            dlsch_interleaving:            0.503 us;              11   | 19                        rx_dft:            0.000 us;               0 |
+20      ulsch_channel_estimation:            0.000 us;               0   | 21  ulsch_freq_offset_estimation:            0.000 us;               0 |
+22                ulsch_decoding:            0.000 us;               0   | 23            ulsch_demodulation:            0.000 us;               0 |
+24         ulsch_rate_unmatching:            0.000 us;               0   | 25          ulsch_turbo_decoding:            0.000 us;               0 |
+26          ulsch_deinterleaving:            0.000 us;               0   | 27          ulsch_demultiplexing:            0.000 us;               0 |
+softmodem> measur cpustats disable
+```
+
+signal processing statistics are always available.
+```bash
+softmodem>  measur show enb   
+--------------------------------- eNB 0 mac stats CC 0 frame 68 ---------------------------------
+           total_num_bcch_pdu =              44                     bcch_buffer =              17               total_bcch_buffer =             937
+                     bcch_mcs =               2              total_num_ccch_pdu =               0                     ccch_buffer =               0
+            total_ccch_buffer =               0                        ccch_mcs =               0              total_num_pcch_pdu =               0
+                  pcch_buffer =               0               total_pcch_buffer =               0                        pcch_mcs =               0
+             num_dlactive_UEs =               0                  available_prbs =              25            total_available_prbs =           16924
+              available_ncces =               0                   dlsch_bitrate =               0                  dlsch_bytes_tx =               0
+                dlsch_pdus_tx =               0             total_dlsch_bitrate =               0            total_dlsch_bytes_tx =               0
+          total_dlsch_pdus_tx =               0                   ulsch_bitrate =               0                  ulsch_bytes_rx =               0
+                ulsch_pdus_rx =               0             total_ulsch_bitrate =               0            total_ulsch_bytes_rx =               0
+          total_ulsch_pdus_rx =               0                 sched_decisions =               0                missed_deadlines =               0
+```
+[oai telnetserver home](telnetsrv.md)
+[oai telnetserver usage home](telnetusage.md)

common/utils/telnetsrv/DOC/telnetusage.md

@@ -5,7 +5,7 @@ By default the embedded telnet server, which is implemented in a shared library,
  cd \<oai repository\>/openairinterface5g
  source oaienv
  cd cmake_targets
- ./build_oai  --build-telnetsrv
+ ./build_oai  --build-lib telnetsrv
 ```
 
 This will create the `libtelnetsrv.so` file in the `targets/bin` and `cmake_targets/lte_build_oai/build` sub directories of the oai repository.
@@ -23,6 +23,7 @@ Below are  examples of telnet sessions:
 *  [using the loop command](telnetloop.md)
 *  [loader command](telnetloader.md)
 *  [log command](telnetlog.md)
+*  [measur command](telnetmeasur.md)
 
 # telnet server parameters
 The telnet server is using the [oai configuration module](Config/Rtusage). Telnet parameters must be specified in the `telnetsrv` section. Some parameters can be modified via the telnet telnet server command, as specified in the last column of the following table.