Merge bitcoin/bitcoin#24746: refactor: remove macOS MAP_ANONYMOUS work around

112a7ab refactor: remove macOS MAP_ANONYMOUS work around (fanquake)

Pull request description:

  This was added to support compilation on macOS 10.10, our minimum
  required macOS is now 10.15. macOS has also supported it since 10.11.

  See bitcoin/bitcoin#9063.

  macOS 12.3 manpage for mmap:
  ```bash
       MAP_ANONYMOUS     Synonym for MAP_ANON.

       MAP_ANON          Map anonymous memory not associated with any specific file.
  ```

ACKs for top commit:
  laanwj:
    Code review ACK 112a7ab
  jarolrod:
    ACK 112a7ab

Tree-SHA512: 920744c755d05d813ab312ff27e42eacb27b1297972800e6fb64bbaad1ea14258751a7dd80c07bfa554a172f36960b26a07505f67e82885253c8bf551073c38e

Author: laanwj

src/support/lockedpool.cpp

@@ -235,12 +235,6 @@ PosixLockedPageAllocator::PosixLockedPageAllocator()
 #endif
 }
 
-// Some systems (at least OS X) do not define MAP_ANONYMOUS yet and define
-// MAP_ANON which is deprecated
-#ifndef MAP_ANONYMOUS
-#define MAP_ANONYMOUS MAP_ANON
-#endif
-
 void *PosixLockedPageAllocator::AllocateLocked(size_t len, bool *lockingSuccess)
 {
     void *addr;