Avoid inlining kwargs check function that only checks for errors and is not worth being inlined.

Also avoid double-check overhead for strigns and string subtypes in Py2: only needed in Py2.6 and not really worth it.

Cython/Utility/FunctionArguments.c

@@ -117,7 +117,7 @@ static void __Pyx_RaiseMappingExpectedError(PyObject* arg) {
 
 //////////////////// KeywordStringCheck.proto ////////////////////
 
-static CYTHON_INLINE int __Pyx_CheckKeywordStrings(PyObject *kwdict, const char* function_name, int kw_allowed); /*proto*/
+static int __Pyx_CheckKeywordStrings(PyObject *kwdict, const char* function_name, int kw_allowed); /*proto*/
 
 //////////////////// KeywordStringCheck ////////////////////
 
@@ -125,7 +125,7 @@ static CYTHON_INLINE int __Pyx_CheckKeywordStrings(PyObject *kwdict, const char*
 //  were passed to a function, or if any keywords were passed to a
 //  function that does not accept them.
 
-static CYTHON_INLINE int __Pyx_CheckKeywordStrings(
+static int __Pyx_CheckKeywordStrings(
     PyObject *kwdict,
     const char* function_name,
     int kw_allowed)
@@ -140,7 +140,7 @@ static CYTHON_INLINE int __Pyx_CheckKeywordStrings(
 #else
     while (PyDict_Next(kwdict, &pos, &key, 0)) {
         #if PY_MAJOR_VERSION < 3
-        if (unlikely(!PyString_CheckExact(key)) && unlikely(!PyString_Check(key)))
+        if (unlikely(!PyString_Check(key)))
         #endif
             if (unlikely(!PyUnicode_Check(key)))
                 goto invalid_keyword_type;