Update changelog for 0.26.3-insiders4: (#4857)

* Update changelog
Authored-by: Colen Garoutte-Carson <[email protected]>

Author: Colengms

Extension/CHANGELOG.md

@@ -1,5 +1,15 @@
 # C/C++ for Visual Studio Code Change Log
 
+## Version 0.26.3-insiders4: January 16, 2020
+### Bug Fixes
+* Update dependent modules to address a security warning due to use of a deprecated API.  [#4381](https://github.com/microsoft/vscode-cpptools/issues/4381)
+* Fix an issue in which files may be unnecessarily removed from the tag parser database on startup, if using a custom configuration provider, resulting in a large number of files being reparsed.  [#4802](https://github.com/microsoft/vscode-cpptools/issues/4802)
+* Fix an issue in which `Build and Debug Active File` would fail to detect a compiler, without a compiler present in `compilerPath`.  [#4834](https://github.com/microsoft/vscode-cpptools/issues/4834)
+* Fix a crash when failing to launch external executables on Linux and Mac.
+
+### Enhancements
+* If clang-format is found in the environment path, that version will take precedence over the copy of clang-format bundled with the extension. [#3569](https://github.com/microsoft/vscode-cpptools/issues/3569)
+
 ## Version 0.26.3-insiders3: January 8, 2020
 ### Bug Fixes
 * Improve memory usage in projects with a large number of files. [#3326](https://github.com/microsoft/vscode-cpptools/issues/3326)