Adapt download script to use svn export instead of viewcvs

This just makes me feel less icky.
Import more file types from glibc 2.18.

Many of these such as networks, protocols, etc. make a lot of sense for
this module since they are usually never customized and thus have little
need to actually be in /etc all the time.
Compile all new file types, update CFLAGS

Fairly simple compile fixes:
 - Get better warnings (-std=gnu99 -Wall)
 - Add a few more includes and stub macros to compat.h
 - Fix symbol names in file-hosts.c
 - Don't export the function defined by LINE_PARSER in files-parse.c
Define new ALTFILES_SYMBOL macros to replace CONCAT

The chaining of CONCAT macros was a bit ugly, this cleans up the changes
required to port files from glibc to altfiles.
Fix the Makefile's build dependencies for included sources.