win: disable stl exception usage

Tell the stl that exception handling is unavailable. This avoids warnings
like:

  C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\include\
  xlocale(337): warning C4530: C++ exception handler used, but unwind
  semantics are not enabled. Specify /EHsc

PR-URL: https://github.com/iojs/io.js/pull/258
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

common.gypi

@@ -179,6 +179,8 @@
           # ... or that C implementations shouldn't use
           # POSIX names
           '_CRT_NONSTDC_NO_DEPRECATE',
+          # Make sure the STL doesn't try to use exceptions
+          '_HAS_EXCEPTIONS=0',
           'BUILDING_V8_SHARED=1',
           'BUILDING_UV_SHARED=1',
         ],