configure: Check for GCC diagnostic pragma support inside of functions

The actual usage of the pragma is within functions and older versions
of gcc only support the pragma outside of functions.

configure

@@ -3779,8 +3779,7 @@ EOF
 done
 
 check_cc <<EOF && enable pragma_deprecated
-_Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"")
+void foo(void) { _Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"") }
-_Pragma("GCC diagnostic warning \"-Wdeprecated-declarations\"")
 EOF
 
 check_cc <<EOF && enable attribute_packed