add msvc build to libteletone

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@632 d0543943-73ff-0310-b7d9-9358b9ac24b2

libs/libteletone/src/libteletone.h

@@ -53,6 +53,14 @@ typedef struct {
 	teletone_process_t freqs[TELETONE_MAX_TONES];
 } teletone_tone_map_t;
 
+#if !defined(M_PI)
+/* C99 systems may not define M_PI */
+#define M_PI 3.14159265358979323846264338327
+#endif
+
+#ifdef _MSC_VER
+#define int16_t __int16
+#endif
 
 #include <libteletone_generate.h>
 #include <libteletone_detect.h>