Merge pull request #552 from stinos/mingw-alloca

py: Use <alloca.h> for alloca()

py/builtinimport.c

 #include <stdint.h>
-#include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 #include <assert.h>
-#ifdef __MINGW32__
-// For alloca()
-#include <malloc.h>
-#endif
+#include <alloca.h>
 
 #include "mpconfig.h"
 #include "nlr.h"

py/objfun.c

 #include <stdbool.h>
-#include <stdlib.h>
 #include <string.h>
 #include <assert.h>
-#ifdef __MINGW32__
-// For alloca()
-#include <malloc.h>
-#endif
+#include <alloca.h>
 
 #include "mpconfig.h"
 #include "nlr.h"

windows/alloca.h

+#include <malloc.h>