[Description]

[Description]
  Scrub MdePkg:
  - Add file description with doxygen format.
  - Add calling convention of library class in MdePkg.
  - Add function descriptions of public protocol/library class.

[Impaction]
  It should be backward-compatible.

[Ref Info]
  N/A

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@4985 6f19259b-4bc3-4df7-8a09-765794883524