Removed SCons warning flags duplication on Windows. It now uses

the same scheme as for gcc on Linux.
Review URL: http://codereview.chromium.org/2424

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@292 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

SConstruct

@@ -63,7 +63,6 @@ LIBRARY_FLAGS = {
   'msvc': {
     'all': {
       'DIALECTFLAGS': ['/nologo'],
-      'WARNINGFLAGS': ['/W3', '/WX', '/wd4355', '/wd4800'],
       'CCFLAGS':      ['$DIALECTFLAGS', '$WARNINGFLAGS'],
       'CXXFLAGS':     ['$CCFLAGS', '/GR-', '/Gy'],
       'CPPDEFINES':   ['WIN32', '_USE_32BIT_TIME_T', 'PCRE_STATIC'],