OptionRomPkg: Add BltLib definition

OptionRomPkg: Add BltLib definition

This library is intended to make it easy to perform blt operations
on a GOP framebuffer without using the GOP Blt function.

There can be two main forms of implementations of this library:
1) A library which interfaces directly with a framebuffer, and
   has no dependence on the GOP protocol.  Once configured with
   the framebuffer parameters, it can operate directly on the
   framebuffer.
2) A library which interfaces with the GOP protocol.  In this
   case this library provides a convenience layer and allows
   blt code to look cleaner.

Potential uses for this library:
* Video driver with a framebuffer will not need to implement
  GOP Blt function itself.  Instead it can utilize an
  implementation of this library as described in #1 above.
* OS Loader code which would like to easily use the GOP framebuffer
  after Exit Boot Services.  This would use a library instance
  as described in #1 above.
* Any other code which would like to call GOP blt, but simplify
  the code with the more convenient functions provided by this
  library interface.  (Using a library as described in #2 above.)

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11520 6f19259b-4bc3-4df7-8a09-765794883524