Temporarily revert "mimalloc: adjust for building inside Git"

In preparation for upgrading to a newer mimalloc version.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

compat/mimalloc/alloc.c

@@ -17,6 +17,7 @@ terms of the MIT license. A copy of the license can be found in the file
 #include <stdlib.h>      // malloc, abort
 
 #define MI_IN_ALLOC_C
+#include "alloc-override.c"
 #include "free.c"
 #undef MI_IN_ALLOC_C
 

compat/mimalloc/mimalloc.h

@@ -95,8 +95,7 @@ terms of the MIT license. A copy of the license can be found in the file
 // Includes
 // ------------------------------------------------------
 
-#include "git-compat-util.h"
-
+#include <stddef.h>     // size_t
 #include <stdbool.h>    // bool
 #include <stdint.h>     // INTPTR_MAX