FS-7966. First pass at moving to Visual Studio 2015.

The new C compiler breaks a lot of things. snprintf and timespec now exist, and redefining causes an error.
Many more things are warnings, so warnings-as-errors will fail - remove it from some projects for now.
V8: don't pass VS version to build batch file.
mod_sofia: Config has too-long if/elseif chain. Break this up to avoid "parser stack overflow; program too complex".
Add mod_conference.h to project and dir to includes.

libs/freetdm/src/include/ftdm_declare.h

@@ -106,7 +106,7 @@ extern "C" {
 #ifndef strncasecmp
 #define strncasecmp(s1, s2, n) _strnicmp(s1, s2, n)
 #endif
-#ifndef snprintf
+#if _MSC_VER < 1900
 #define snprintf _snprintf
 #endif
 #ifndef S_IRUSR