libcompat.h: rename several functions if the _ variant exists
libcompat.h: rename several functions if the _ variant exists

For fileno, getpid, pipe, putenv, read, strdup, and write,
if the name append with _ exists, use that instead.
This likely only applied to MSVC.

git-svn-id: ae38cf1093b87151f738d2b2220cac7742ad2e55@933 64e312b2-a51f-0410-8e61-82d0ca0eb02a

lubosz/check,lubosz/check,lubosz/check,lubosz/check