Fixing/disabling Windows x64 warnings

Disabled MSVC #4267 warnings in common.gypi to enable x64 builds
for Windows.
Fixed MSVC #4267 warnings in test/testsupport.
Added third_party/directxsdk to .gitignore.

With http://review.webrtc.org/1070008 landed, this should make it possible
to build for x64 on Windows.

BUG=1348
TEST=Compiling with http://review.webrtc.org/1070008 applied:
set GYP_DEFINES="target_arch=x64"
set GYP_GENERATORS=ninja
gclient sync
ninja -C out\Debug_x64

Review URL: https://webrtc-codereview.appspot.com/1060008

git-svn-id: http://webrtc.googlecode.com/svn/trunk@3464 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/audio_coding/neteq4/neteq.gypi

@@ -113,6 +113,10 @@
         'time_stretch.cc',
         'time_stretch.h',
       ],
+      # Disable warnings to enable Win64 build, issue 1323.
+      'msvs_disabled_warnings': [
+        4267,  # size_t to int truncation.
+      ],
     },
   ], # targets
   'conditions': [
@@ -144,7 +148,11 @@
             'audio_decoder.cc',
             'interface/audio_decoder.h',
           ],
-        }, # audio_decoder_unittest
+          # Disable warnings to enable Win64 build, issue 1323.
+          'msvs_disabled_warnings': [
+            4267,  # size_t to int truncation.
+          ],
+        }, # audio_decoder_unittests
 
         {
           'target_name': 'neteq_unittest_tools',
@@ -168,6 +176,10 @@
             'tools/rtp_generator.cc',
             'tools/rtp_generator.h',
           ],
+          # Disable warnings to enable Win64 build, issue 1323.
+          'msvs_disabled_warnings': [
+            4267,  # size_t to int truncation.
+          ],
         }, # neteq_unittest_tools
       ], # targets
     }], # include_tests