NGHTTP2_VERSION_NUM: have configure generate the define

configure.ac

 dnl nghttp2 - HTTP/2.0 C Library
 
-dnl Copyright (c) 2012 Tatsuhiro Tsujikawa
+dnl Copyright (c) 2012, 2013 Tatsuhiro Tsujikawa
 
 dnl Permission is hereby granted, free of charge, to any person obtaining
 dnl a copy of this software and associated documentation files (the
@@ -30,6 +30,14 @@ AC_SUBST(LT_CURRENT, 0)
 AC_SUBST(LT_REVISION, 0)
 AC_SUBST(LT_AGE, 0)
 
+major=`echo $PACKAGE_VERSION |cut -d. -f1 | sed -e "s/[^0-9]//g"`
+minor=`echo $PACKAGE_VERSION |cut -d. -f2 | sed -e "s/[^0-9]//g"`
+patch=`echo $PACKAGE_VERSION |cut -d. -f3 | cut -d- -f1 | sed -e "s/[^0-9]//g"`
+
+PACKAGE_VERSION_NUM=`printf "0x%02x%02x%02x" "$major" "$minor" "$patch"`
+
+AC_SUBST(PACKAGE_VERSION_NUM)
+
 AC_CANONICAL_BUILD
 AC_CANONICAL_HOST
 AC_CANONICAL_TARGET

lib/includes/nghttp2/nghttp2ver.h.in

 /*
  * nghttp2 - HTTP/2.0 C Library
  *
- * Copyright (c) 2012 Tatsuhiro Tsujikawa
+ * Copyright (c) 2012, 2013 Tatsuhiro Tsujikawa
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -31,4 +31,12 @@
  */
 #define NGHTTP2_VERSION "@PACKAGE_VERSION@"
 
+/**
+ * @macro
+ * Numerical representation of the version number of the nghttp2 library
+ * release. This is a 24 bit number with 8 bits for major number, 8 bits
+ * for minor and 8 bits for patch. Version 1.2.3 becomes 0x010203.
+ */
+#define NGHTTP2_VERSION_NUM @PACKAGE_VERSION_NUM@
+
 #endif /* NGHTTP2VER_H */