Update Linux CentOS 7 ports to 7.3.1611. While 7.2 had semi-official i386
packages there are no such packages for 7.3 yet so i386 support has been
marked IGNORE for now.
Change DIST_SUBDIR to just "centos" so distfiles that remain the same
between major versions don't have to be redownloaded.
Remove fmake hacks from linux.mk.
Submitted by: Piotr Kubaj <pkubaj@anongoth.pl>
Since base r283461 /compat/linux/dev/shm must point to a tmpfs. Make
/compat/linux/dev/shm a plain directory instead of a link to /tmp so we
don't force users to mount tmpfs on /tmp. This also makes /dev/shm a
separate namespace from /tmp.
Add libffi, needed by glib2.
PR: 207769