define __CHAR_BIT__ for Mac (#1564)

* define `__CHAR_BIT__` for Mac
* update changelog

Author: bobbrow

Extension/CHANGELOG.md

@@ -10,6 +10,7 @@
 * Fix error popup appearing with non-workspace files when using `compile_commands.json`. [#1475](https://github.com/Microsoft/vscode-cpptools/issues/1475)
 * Fix snippet completions being blocked after `#`. [#1531](https://github.com/Microsoft/vscode-cpptools/issues/1531)
 * Add more macros to `cpp.hint` (fixing missing symbols).
+* Add `__CHAR_BIT__=8` to default defines on Mac. [#1510](https://github.com/Microsoft/vscode-cpptools/issues/1510)
 * Added support for config variables to `c_cpp_properties.json`. [#314](https://github.com/Microsoft/vscode-cpptools/issues/314)
   * Joshua Cannon (@thejcannon) [PR #1529](https://github.com/Microsoft/vscode-cpptools/pull/1529)
 * Define `_UNICODE` by default on Windows platforms. [#1538](https://github.com/Microsoft/vscode-cpptools/issues/1538)

Extension/bin/msvc.64.darwin.json

@@ -2,7 +2,8 @@
     "defaults": [
       "--clang",
       "--pack_alignment",
-      "8"
+      "8",
+      "-D__CHAR_BIT__=8"
     ],
     "defaults_op" :  "merge"
   }