Add vim dependency (for xxd tool)

README

@@ -29,6 +29,7 @@ Compilation and installation
 * Required dependencies:
 	- oRTP
 	- libspeex and libspeexdsp
+	- vim
 * Optional dependencies (for video to be enabled, see --enable-video):
 	- libavcodec
 	- libswscale

configure.ac

@@ -1027,7 +1027,7 @@ AM_CONDITIONAL(WITH_EPM,test $EPM != false && test $MKEPMLIST != false && test $
 dnl Check for xxd
 AC_CHECK_PROG(xxd_found, xxd, yes)
 if test "$xxd_found" != yes ;then
- 	AC_MSG_ERROR("xxd is required")
+ 	AC_MSG_ERROR("xxd is required (provided by vim package)")
 fi
 
 # Preferred packaging system, as per EPM terminology