Implement support for non-coalescing maps on MinGW.

- Do not reallocate huge objects in place if the number of backing
  chunks would change.
- Do not cache multi-chunk mappings.

This resolves #213.

include/jemalloc/internal/jemalloc_internal_defs.h.in

@@ -169,6 +169,15 @@
 /* One page is 2^LG_PAGE bytes. */
 #undef LG_PAGE
 
+/*
+ * If defined, adjacent virtual memory mappings with identical attributes
+ * automatically coalesce, and they fragment when changes are made to subranges.
+ * This is the normal order of things for mmap()/munmap(), but on Windows
+ * VirtualAlloc()/VirtualFree() operations must be precisely matched, i.e.
+ * mappings do *not* coalesce/fragment.
+ */
+#undef JEMALLOC_MAPS_COALESCE
+
 /*
  * If defined, use munmap() to unmap freed chunks, rather than storing them for
  * later reuse.  This is disabled by default on Linux because common sequences