Rename "GCC_DIAGNOSTIC" macro to make it Cython specific and make it available...

Rename "GCC_DIAGNOSTIC" macro to make it Cython specific and make it available to other utility code sections.

Cython/Utility/TypeConversion.c

@@ -430,6 +430,15 @@ static CYTHON_INLINE PyObject * __Pyx_PyInt_FromSize_t(size_t ival) {
 }
 
 
+/////////////// GCCDiagnostics.proto ///////////////
+
+// GCC diagnostic pragmas were introduced in GCC 4.6
+// Used to silence conversion warnings that are ok but cannot be avoided.
+#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6))
+#define __Pyx_HAS_GCC_DIAGNOSTIC
+#endif
+
+
 /////////////// ToPyCTupleUtility.proto ///////////////
 static PyObject* {{funcname}}({{struct_type_decl}});
 
@@ -687,6 +696,7 @@ static CYTHON_INLINE PyObject* {{TO_PY_FUNCTION}}({{TYPE}} value, Py_ssize_t wid
 /////////////// CIntToPyUnicode ///////////////
 //@requires: StringTools.c::BuildPyUnicode
 //@requires: CIntToDigits
+//@requires: GCCDiagnostics
 
 #ifdef _MSC_VER
     #ifndef _MSC_STDINT_H_
@@ -702,10 +712,6 @@ static CYTHON_INLINE PyObject* {{TO_PY_FUNCTION}}({{TYPE}} value, Py_ssize_t wid
 
 // NOTE: inlining because most arguments are constant, which collapses lots of code below
 
-// GCC diagnostic pragmas were introduced in GCC 4.6
-#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6))
-#define GCC_DIAGNOSTIC
-#endif
 static CYTHON_INLINE PyObject* {{TO_PY_FUNCTION}}({{TYPE}} value, Py_ssize_t width, char padding_char, char format_char) {
     // simple and conservative C string allocation on the stack: each byte gives at most 3 digits, plus sign
     char digits[sizeof({{TYPE}})*3+2];
@@ -715,12 +721,12 @@ static CYTHON_INLINE PyObject* {{TO_PY_FUNCTION}}({{TYPE}} value, Py_ssize_t wid
     Py_ssize_t length, ulength;
     int prepend_sign, last_one_off;
     {{TYPE}} remaining;
-#ifdef GCC_DIAGNOSTIC
+#ifdef __Pyx_HAS_GCC_DIAGNOSTIC
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wconversion"
 #endif
     const {{TYPE}} neg_one = ({{TYPE}}) -1, const_zero = ({{TYPE}}) 0;
-#ifdef GCC_DIAGNOSTIC
+#ifdef __Pyx_HAS_GCC_DIAGNOSTIC
 #pragma GCC diagnostic pop
 #endif
     const int is_unsigned = neg_one > const_zero;