Adding support for custom rc header formatting.

Adding ability to overwride the default rc header file format
to be able to replace the default:
with:

This is needed to be able to collect the symbols that get used during
the compilation step.

BUG=338759

Original patch by aurimas@chromium.org, issue 171863002.

Review URL: https://codereview.chromium.org/172533003

git-svn-id: http://grit-i18n.googlecode.com/svn/trunk@152 7262f16d-afe8-6277-6482-052fa10e57b1