[llvm-rc] Serialize CURSOR and ICON resources to .res

This is part 6 of llvm-rc serialization.

This adds ability to output cursors and icons as resources.

Unfortunately, we can't just copy .cur or .ico files to output - as each
file might contain multiple images, each of them needs to be unpacked
and stored as a separate resource. This forces us to parse cursor and
icon contents. (Fortunately, these formats are pretty similar and can be
processed by mostly common code).

As test files are binary, here is a short explanation of .cur and .ico
files stored:

cursor.cur, cursor-8.cur, cursor-32.cur are sample correct cursor files,
differing in their bit depth.

icon-old.ico, icon-new.ico are sample correct icon files;

icon-png.ico is a sample correct icon file in PNG format (instead of
usual BMP);

cursor-eof.cur is an incorrect cursor file - this is cursor.cur with
some of its final bytes removed.

cursor-bad-offset.cur is an incorrect cursor file - image header states
that image data begins at offset 0xFFFFFFFF.

Sample correct cursors and icons were created by Nico Weber.

Patch by Marek Sokolowski
Differential Revision: https://reviews.llvm.org/D37878

llvm-svn: 315109