Clean up fpathconf(3)/pathconf(3).

fpathconf(3) and pathconf(3) can share code. There's no such
header file as <pathconf.h>. glibc/POSIX and BSD disagree about where
the _POSIX_* definitions should go.

Change-Id: I4a67f1595c9f5fbb26700a131178eedebd6bf712
9 files changed