Revert "Make memorypool threadsafe "

src/mempool.c

@@ -21,12 +21,6 @@
 #endif
 #include "mempool.h"
 
-#ifdef _MSC_VER
-#define THREAD_LOCAL __declspec(thread)
-#else
-#define THREAD_LOCAL __thread
-#endif
-
 /*
 **  ALLOC_BLOCK_SIZE - adjust this size to suit your installation - it
 **  should be reasonably large otherwise you will be mallocing a lot.
@@ -60,7 +54,7 @@ typedef struct alloc_root_s
 **  root - Pointer to the current pool.
 */
 
-THREAD_LOCAL alloc_root_t *root;
+static alloc_root_t *root;
 
 
 /*