[Docs] Modernize references to macOS

Summary:
This updates all places in documentation that refer to "Mac OS X", "OS X", etc.
to instead use the modern name "macOS" when no specific version number is
mentioned.

If a specific version is mentioned, this attempts to use the OS name at the time
of that version:

* Mac OS X for 10.0 - 10.7
* OS X for 10.8 - 10.11
* macOS for 10.12 - present

Reviewers: JDevlieghere

Subscribers: mgorny, christof, arphaman, cfe-commits, lldb-commits, libcxx-commits, llvm-commits

Tags: #clang, #lldb, #libc, #llvm

Differential Revision: https://reviews.llvm.org/D62654

llvm-svn: 362113
diff --git a/llvm/docs/DebuggingJITedCode.rst b/llvm/docs/DebuggingJITedCode.rst
index d6101d5..fad4c9b 100644
--- a/llvm/docs/DebuggingJITedCode.rst
+++ b/llvm/docs/DebuggingJITedCode.rst
@@ -29,7 +29,7 @@
 In order to debug code JIT-ed by LLVM, you need GDB 7.0 or newer, which is
 available on most modern distributions of Linux.  The version of GDB that
 Apple ships with Xcode has been frozen at 6.3 for a while.  LLDB may be a
-better option for debugging JIT-ed code on Mac OS X.
+better option for debugging JIT-ed code on macOS.
 
 
 Debugging MCJIT-ed code