Add support for the GN configuration language (#3368)

* Add samples and definition for GN build files

* Add grammar to provide GN syntax highlighting

* Fix failing tests

* Add Python extensions for GYP includes and .gclient configs

lib/linguist/languages.yml

@@ -19,7 +19,7 @@
 # language_id       - Integer used as a language-name-independent indexed field so that we can rename
 #                     languages in Linguist without reindexing all the code on GitHub. Must not be
 #                     changed for existing languages without the explicit permission of GitHub staff.
-# color             - CSS hex color to represent the language. Only used if type is "programming" or "prose"
+# color             - CSS hex color to represent the language. Only used if type is "programming" or "prose".
 # tm_scope          - The TextMate scope that represents this programming
 #                     language. This should match one of the scopes listed in
 #                     the grammars.yml file. Use "none" if there is no grammar
@@ -1393,6 +1393,18 @@ GLSL:
   - ".vshader"
   ace_mode: glsl
   language_id: 124
+GN:
+  type: data
+  extensions:
+  - ".gn"
+  - ".gni"
+  interpreters:
+  - gn
+  tm_scope: source.gn
+  ace_mode: python
+  codemirror_mode: python
+  codemirror_mime_type: text/x-python
+  language_id: 302957008
 Game Maker Language:
   type: programming
   color: "#8fb200"
@@ -3392,6 +3404,7 @@ Python:
   - ".cgi"
   - ".fcgi"
   - ".gyp"
+  - ".gypi"
   - ".lmi"
   - ".py3"
   - ".pyde"
@@ -3404,6 +3417,7 @@ Python:
   - ".wsgi"
   - ".xpy"
   filenames:
+  - .gclient
   - BUCK
   - BUILD
   - SConscript