Squashed 'src/leveldb/' changes from 64052c76c5..524b7e36a8

524b7e36a8 Merge #19: Increase maximum read-only mmap()s used from 1000 to 4096 on 64-bit systems
4874cb8d3e Increase maximum number of read-only mmap()s used from 1000 to 4096 on 64 bit systems.

git-subtree-dir: src/leveldb
git-subtree-split: 524b7e36a8e3bce6fcbcd1b5df09024283f325ba

util/env_posix.cc

@@ -585,8 +585,8 @@ static int MaxMmaps() {
   if (mmap_limit >= 0) {
     return mmap_limit;
   }
-  // Up to 1000 mmaps for 64-bit binaries; none for smaller pointer sizes.
+  // Up to 4096 mmaps for 64-bit binaries; none for smaller pointer sizes.
-  mmap_limit = sizeof(void*) >= 8 ? 1000 : 0;
+  mmap_limit = sizeof(void*) >= 8 ? 4096 : 0;
   return mmap_limit;
 }