Fixes a slew of compiler warnings and turns on "warning as error" in the scons build.

scons/SConscript

@@ -105,9 +105,19 @@ GtestTest = gtest_exports['GtestTest']
 gtest_common_exports = SConscript(GTEST_DIR + '/scons/SConscript.common')
 EnvCreator = gtest_common_exports['EnvCreator']
 
-# TODO(vladl@google.com): restore warnings as errors once all warnings are fixed
-# in gMock.
-env = EnvCreator.Create(env, EnvCreator.WarningOk)
+env = env.Clone()
+if env['PLATFORM'] == 'win32':
+  env.Append(CCFLAGS=[
+      '-wd4127',  # Disables warning "conditional expression is constant",
+                  # triggered by VC 8.0's own STL header <list>.
+      '-wd4702',  # Disables warning "unreachable code", triggered by VC
+                  # 7.1's own STL header <xtree>.
+      '-wd4675',  # Disables warning "resolved overload was found by
+                  # argument-dependent lookup" generated by VC 7.1.
+                  # It just says that VC 7.1 fixed a bug in earlier
+                  # versions of VC so the code behavior will be
+                  # different than compiled with VC 6.0, for example.
+      ])
 
 # Note: The relative paths in SConscript files are relative to the location
 # of the SConscript file itself. To make a path relative to the location of