cmake: Correctly check for *snprintf functions on Windows

BUG: https://red.libssh.org/issues/205

Signed-off-by: Andreas Schneider <asn@cryptomilk.org>

ConfigureChecks.cmake

@@ -125,16 +125,19 @@ endif (NOT WITH_GCRYPT)
 check_function_exists(isblank HAVE_ISBLANK)
 check_function_exists(strncpy HAVE_STRNCPY)
 
-check_symbol_exists(vsnprintf "stdio.h" HAVE_VSNPRINTF)
-check_symbol_exists(snprintf "stdio.h" HAVE_SNPRINTF)
+if (NOT WIN32)
+  check_function_exists(vsnprintf HAVE_VSNPRINTF)
+  check_function_exists(snprintf HAVE_SNPRINTF)
+endif (NOT WIN32)
 
 if (WIN32)
-    check_function_exists(_strtoui64 HAVE__STRTOUI64)
+    check_symbol_exists(vsnprintf "stdio.h" HAVE_VSNPRINTF)
+    check_symbol_exists(snprintf "stdio.h" HAVE_SNPRINTF)
 
-    check_function_exists(_vsnprintf_s HAVE__VSNPRINTF_S)
-    check_function_exists(_vsnprintf HAVE__VSNPRINTF)
-    check_function_exists(_snprintf HAVE__SNPRINTF)
-    check_function_exists(_snprintf_s HAVE__SNPRINTF_S)
+    check_symbol_exists(_vsnprintf_s "stdio.h" HAVE__VSNPRINTF_S)
+    check_symbol_exists(_vsnprintf "stdio.h" HAVE__VSNPRINTF)
+    check_symbol_exists(_snprintf "stdio.h" HAVE__SNPRINTF)
+    check_symbol_exists(_snprintf_s "stdio.h" HAVE__SNPRINTF_S)
 
     if (HAVE_WSPIAPI_H OR HAVE_WS2TCPIP_H)
         check_symbol_exists(ntohll winsock2.h HAVE_NTOHLL)
@@ -148,6 +151,8 @@ if (WIN32)
         set(CMAKE_REQUIRED_LIBRARIES)
     endif (HAVE_WSPIAPI_H OR HAVE_WS2TCPIP_H)
 
+    check_function_exists(_strtoui64 HAVE__STRTOUI64)
+
     set(HAVE_SELECT TRUE)
 else (WIN32)
     check_function_exists(poll HAVE_POLL)