AppPkg/.../Python-2.7.10: Rename identifiers beginning with "posix_" to "edk2_".

AppPkg/.../Python-2.7.10: Rename identifiers beginning with "posix_" to "edk2_".

Rename identifiers to have an edk2_ prefix instead of posix_ in order to
conform to the convention used in other environment-specific Python modules.
This also makes the names match the module instead of implying that these are
Posix compatible routines.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Daryl McDaniel <edk2-lists@mc2research.org>
Reviewed-by: Erik Bjorge <erik.c.bjorge@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19460 6f19259b-4bc3-4df7-8a09-765794883524