Disable -Werror on OSX and remove unnecessary patches

This disables -Werror and removes all the patches that silence specific
warnings.

Author: ignisf

patches/clang/no-unused-private-field.patch

@@ -0,0 +1,12 @@
+diff --git a/build/standalone.gypi b/build/standalone.gypi
+index 125c5bf..de1924c 100644
+--- a/build/standalone.gypi
++++ b/build/standalone.gypi
+@@ -194,7 +194,6 @@
+           'GCC_INLINES_ARE_PRIVATE_EXTERN': 'YES',
+           'GCC_SYMBOLS_PRIVATE_EXTERN': 'YES',      # -fvisibility=hidden
+           'GCC_THREADSAFE_STATICS': 'NO',           # -fno-threadsafe-statics
+-          'GCC_TREAT_WARNINGS_AS_ERRORS': 'YES',    # -Werror
+           'GCC_VERSION': 'com.apple.compilers.llvmgcc42',
+           'GCC_WARN_ABOUT_MISSING_NEWLINE': 'YES',  # -Wnewline-eof
+           # MACOSX_DEPLOYMENT_TARGET maps to -mmacosx-version-min