Test for Asterisk Version info

Doxygen uses the ASTERISKVERSION as a sub header. If a SVN export is done and no .svn or .version file exists it defualts to UNKNOWN__and_probably_unsupported which is honest but not great for the online docs.  During the "make progdocs" I added a test for this and just warned and ommitted the version.

(issue ASTERISK-20259)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@374949 65c4cc65-6c06-0410-ace0-fbb531ad65f3

Makefile

@@ -747,7 +747,11 @@ else
 	@sed -i "/^HAVE_DOT/s/NO/YES/" contrib/asterisk-ng-doxygen
 endif
 	# Set Doxygen PROJECT_NUMBER variable
+ifneq ($(ASTERISKVERSION),UNKNOWN__and_probably_unsupported)
 	@sed -i "/^PROJECT_NUMBER/s/PROJECT_NUMBER.*/PROJECT_NUMBER = "$(ASTERISKVERSION)"/" contrib/asterisk-ng-doxygen
+else
+	echo "Asterisk Version is unknown, not configuring Doxygen PROJECT_NUMBER."
+endif
 	# Validate Doxygen Configuration
 	@doxygen -u contrib/asterisk-ng-doxygen
 	# Run Doxygen