hppa: Remove warnings and fix conformance errors.

(1) Fix warnings.

This is a bulk update to fix all the warnings that were causing
build failures with -Werror on hppa.

The most egregious problems are in dl-fptr.c which needs to be
entirely rewritten, thus I've used -Wno-error for that.

(2) Fix conformance errors.

The sysdep.c file had __syscall_error and syscall in one file
which caused conformance issues by including syscall when
__syscall_error was linked to. The fix is obviously to split
the file and use syscall.c to implement syscall.