Delete old video defines in engine config.

This CL deletes the old and not used video defines in
engine_configurations.h and pre-pends voice_ to indicate there are only
voice/audio defines left in the file.

BUG=none
R=solenberg@webrtc.org

Review URL: https://codereview.webrtc.org/2401673002 .

Cr-Original-Commit-Position: refs/heads/master@{#14558}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 7056be937f040e8d794b6f733e1eb409a62dceef
diff --git a/common.gyp b/common.gyp
index 3b5fe90..ad3f9f2 100644
--- a/common.gyp
+++ b/common.gyp
@@ -16,8 +16,8 @@
         'common_types.h',
         'config.h',
         'config.cc',
-        'engine_configurations.h',
         'typedefs.h',
+        'voice_engine_configurations.h',
       ],
     },
   ],