Do not require a program to compile/run to check for version coherency

configure.ac

@@ -35,13 +35,11 @@ req=""
 
 # Check version number coherency between RtAudio.h and configure.ac
 AC_MSG_CHECKING([that version numbers are coherent])
-AC_RUN_IFELSE(
-   [AC_LANG_PROGRAM([#include <string.h>
-                     `grep "define RTAUDIO_VERSION" $srcdir/RtAudio.h`],
-                    [return strcmp(RTAUDIO_VERSION, PACKAGE_VERSION);])],
-   [AC_MSG_RESULT([yes])],
-   [AC_MSG_FAILURE([testing RTAUDIO_VERSION==PACKAGE_VERSION failed, check that RtAudio.h defines RTAUDIO_VERSION as "$PACKAGE_VERSION" or that the first line of configure.ac has been updated.])])
-
+RTAUDIO_VERSION=`sed -n 's/#define RTAUDIO_VERSION "\(.*\)"/\1/p' $srcdir/RtAudio.h`
+AS_IF(
+   [test "x$RTAUDIO_VERSION" != "x$PACKAGE_VERSION"],
+   [AC_MSG_FAILURE([testing RTAUDIO_VERSION==PACKAGE_VERSION failed, check that RtAudio.h defines RTAUDIO_VERSION as "$PACKAGE_VERSION" or that the first line of configure.ac has been updated.])]
+)
 # Enable some nice automake features if they are available
 m4_ifdef([AM_MAINTAINER_MODE], [AM_MAINTAINER_MODE])
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])