1) Replace MACRO with C functions.

1) Replace MACRO with C functions.
2) Add HEADER_VALID_ONLY state of variable, which represents only the header is valid and the data/name is stale. This may be caused by incomplete data updating. Adding the state helps to check whether the header is valid. If variable header is valid, then we must skip the data of variable with the valid size. If the header is invalid, we should only skip the header of variable.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@4555 6f19259b-4bc3-4df7-8a09-765794883524