res_pjsip,compat: INFINITY and NAN undefined

On some systems the values for INFINITY and NAN are not defined thus causing
a build error on those systems.  Added definitions for those if they had
not previously been defined.

(closes issue ASTERISK-23056)
Reported by: capouch
Patches:
     inf-nan-patch.txt uploaded by capouch (license 6564)


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/12@406788 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/compat.h

@@ -224,4 +224,12 @@ float roundf(float x);
 #endif
 #endif
 
+#ifndef INFINITY
+#define INFINITY (1.0/0.0)
+#endif
+
+#ifndef NAN
+#define NAN (0.0/0.0)
+#endif
+
 #endif