[docs] Update LeakSanitizer documentation to reflect OS X support

docs/AddressSanitizer.rst

 ``ASAN_OPTIONS=check_initialization_order=1``.
 
 Note that this option is not supported on OS X.
 
 Memory leak detection
 ---------------------
 
 For more information on leak detector in AddressSanitizer, see
-:doc:`LeakSanitizer`. The leak detection is turned on by default on Linux;
+:doc:`LeakSanitizer`. The leak detection is turned on by default on Linux,
+and can be enabled using ``ASAN_OPTIONS=detect_leaks=1`` on OS X;
 however, it is not yet supported on other platforms.
 
 Issue Suppression
 =================
 
 AddressSanitizer is not expected to produce false positives. If you see one,
 look again; most likely it is a true positive!
 

docs/LeakSanitizer.rst

 :doc:`AddressSanitizer` to get both memory error and leak detection, or
 used in a stand-alone mode. LSan adds almost no performance overhead
 until the very end of the process, at which point there is an extra leak
 detection phase.
 
 Usage
 =====
 
-LeakSanitizer is only supported on x86\_64 Linux. In order to use it,
+LeakSanitizer is supported on x86\_64 Linux and OS X. In order to use it,
 simply build your program with :doc:`AddressSanitizer`:
 
 .. code-block:: console
 
     $ cat memory-leak.c
     #include <stdlib.h>
     void *p;
     int main() {
       p = malloc(7);
       p = 0; // The memory is leaked here.
       return 0;
     }
-    % clang -fsanitize=address -g memory-leak.c ; ./a.out
+    % clang -fsanitize=address -g memory-leak.c ; ASAN_OPTIONS=detect_leaks=1 ./a.out
     ==23646==ERROR: LeakSanitizer: detected memory leaks
     Direct leak of 7 byte(s) in 1 object(s) allocated from:
         #0 0x4af01b in __interceptor_malloc /projects/compiler-rt/lib/asan/asan_malloc_linux.cc:52:3
         #1 0x4da26a in main memory-leak.c:4:7
         #2 0x7f076fd9cec4 in __libc_start_main libc-start.c:287
     SUMMARY: AddressSanitizer: 7 byte(s) leaked in 1 allocation(s).
 
 To use LeakSanitizer in stand-alone mode, link your program with
 ``-fsanitize=leak`` flag. Make sure to use ``clang`` (not ``ld``) for the
 link step, so that it would link in proper LeakSanitizer run-time library
 into the final executable.
 
 More Information
 ================
 
 `<https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer>`_