Update manual pages

doc/h2load.1

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-.TH "H2LOAD" "1" "Feb 27, 2018" "1.31.0" "nghttp2"
+.TH "H2LOAD" "1" "May 07, 2018" "1.32.0-DEV" "nghttp2"
 .SH NAME
 h2load \- HTTP/2 benchmarking tool
 .
@@ -155,7 +155,7 @@ example,  with   \fI\%\-t\fP2  and   \fI\%\-r\fP4,  each  thread   gets  2
 connections per period.  When the rate is 0, the program
 will run  as it  normally does, creating  connections at
 whatever variable rate it  wants.  The default value for
-this option is 0.
+this option is 0.  \fI\%\-r\fP and \fI\%\-D\fP are mutually exclusive.
 .UNINDENT
 .INDENT 0.0
 .TP
@@ -170,7 +170,8 @@ option is 1s.
 .TP
 .B \-D, \-\-duration=<N>
 Specifies the main duration for the measurements in case
-of timing\-based benchmarking.
+of timing\-based  benchmarking.  \fI\%\-D\fP  and \fI\%\-r\fP  are mutually
+exclusive.
 .UNINDENT
 .INDENT 0.0
 .TP

doc/h2load.1.rst

@@ -124,7 +124,7 @@ OPTIONS
     connections per period.  When the rate is 0, the program
     will run  as it  normally does, creating  connections at
     whatever variable rate it  wants.  The default value for
-    this option is 0.
+    this option is 0.  :option:`-r` and :option:`\-D` are mutually exclusive.
 
 .. option:: --rate-period=<DURATION>
 
@@ -137,7 +137,8 @@ OPTIONS
 .. option:: -D, --duration=<N>
 
     Specifies the main duration for the measurements in case
-    of timing-based benchmarking.
+    of timing-based  benchmarking.  :option:`-D`  and :option:`\-r`  are mutually
+    exclusive.
 
 .. option:: --warm-up-time=<DURATION>
 

doc/nghttp.1

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-.TH "NGHTTP" "1" "Feb 27, 2018" "1.31.0" "nghttp2"
+.TH "NGHTTP" "1" "May 07, 2018" "1.32.0-DEV" "nghttp2"
 .SH NAME
 nghttp \- HTTP/2 client
 .

doc/nghttpd.1

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-.TH "NGHTTPD" "1" "Feb 27, 2018" "1.31.0" "nghttp2"
+.TH "NGHTTPD" "1" "May 07, 2018" "1.32.0-DEV" "nghttp2"
 .SH NAME
 nghttpd \- HTTP/2 server
 .

doc/nghttpx.1

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-.TH "NGHTTPX" "1" "Feb 27, 2018" "1.31.0" "nghttp2"
+.TH "NGHTTPX" "1" "May 07, 2018" "1.32.0-DEV" "nghttp2"
 .SH NAME
 nghttpx \- HTTP/2 proxy
 .