Generate version number in Doxyfile with configure.

configure.ac

@@ -2,7 +2,7 @@
 AC_INIT(RtAudio, 4.1, gary@music.mcgill.ca, rtaudio)
 AC_CONFIG_AUX_DIR(config)
 AC_CONFIG_SRCDIR(RtAudio.cpp)
-AC_CONFIG_FILES([rtaudio-config librtaudio.pc Makefile tests/Makefile])
+AC_CONFIG_FILES([rtaudio-config librtaudio.pc Makefile tests/Makefile doc/doxygen/Doxyfile])
 
 # Fill GXX with something before test.
 AC_SUBST( GXX, ["no"] )

doc/doxygen/Doxyfile → doc/doxygen/Doxyfile.in

@@ -32,7 +32,7 @@ PROJECT_NAME           = RtAudio
 # This could be handy for archiving the generated documentation or 
 # if some version control system is used.
 
-PROJECT_NUMBER         = 4.1.1
+PROJECT_NUMBER         = @PACKAGE_VERSION@
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description 
 # for a project that appears at the top of each page and should give viewer