- new definition to replace hardcoded values

limit dl_DataToUL_ACK to the number of slots per frame to avoid the need to resize VRB_map and UL_tti_req_ahead

Almost all targets used both SIMU and SIMU_COMMON. So instead of
linking one in the other, this commit merges both libraries into a
common SIMU lib.  Further, we never load SIMU dynamically -- hence
make it a static library.

Also, this commit cleans up CMakeLists.txt to prevent multiple
compilations of taus.c

- The qsort() function is defined as:
  void qsort(void *base, size_t nmemb, size_t size,
    int (*compar)(const void *, const void *));
  and sorts an array with nmemb elements of size size.
- in the gNB scheduling functions, nmemb and size were swapped
- this was causing a stack overflow ending with a SEGFAULT under certain circumstances

- this defition is obsolete

Direct check on dlsim buffer

full symbol buffer will be written bt DFT

removed gNB_id and slot from function calls where proc is used.

--Removed NR_UE_PDSCH global structure
--Changed UE scope to accomodate local PDSCH data
--Removed common_vars.rxdataF from global structure