Fixed the OpenAL-Soft CMakeLists.txt file to work with Visual Studio 2015.

libs/openal-soft/CMakeLists.txt

@@ -434,7 +434,7 @@ IF(NOT HAVE_STRNCASECMP)
     ADD_DEFINITIONS(-Dstrncasecmp=_strnicmp)
 ENDIF()
 
-CHECK_FUNCTION_EXISTS(snprintf HAVE_SNPRINTF)
+CHECK_SYMBOL_EXISTS(snprintf stdio.h HAVE_SNPRINTF)
 IF(NOT HAVE_SNPRINTF)
     CHECK_FUNCTION_EXISTS(_snprintf HAVE__SNPRINTF)
     IF(NOT HAVE__SNPRINTF)
@@ -1254,4 +1254,4 @@ ENDIF()
 
 IF(MEGA)
     install(TARGETS ${LIBNAME} RUNTIME DESTINATION . LIBRARY DESTINATION .)
-ENDIF()
+ENDIF()