Rather than generating enum classes by hand (and complaining in each
file that "this should really be standard"), use glib-mkenums.
Unfortunately, we need a very new version of glib-mkenums in order to
deal with NM's naming conventions and to fix a few other bugs, so just
import that into the source tree temporarily.
Also, to simplify the use of glib-mkenums, import Makefile.glib from
https://bugzilla.gnome.org/654395.
To avoid having to run glib-mkenums for every subdirectory of src/,
add a new "generated" directory, and put the generated enums files
there.
Finally, use Makefile.glib for marshallers too, and generate separate
ones for libnm-glib and NetworkManager.
The current check caught stuff in the .ver file that was outdated, but
didn't quite get stuff that was supposed to be exported but wasn't,
in some cases. Update the regex to ensure that symbols that are
not exported, but that start with "nm_" (and aren't GObject
boilerplate) get flagged during the check.
Update internal code to return to a previous pattern of treating symbols
that start with "_" internal, and expecting symbols that start with
"nm_" to be exported.
Also fixes cases where random glibc symbols would get flagged:
00040ff4 l O *ABS* 00000000 .hidden _GLOBAL_OFFSET_TABLE_
00041380 l O .data 00000000 .hidden __dso_handle
000406e8 l O .dtors 00000000 .hidden __DTOR_END__
0000fbe4 l F .text 00000000 .hidden __i686.get_pc_thunk.cx
0002f980 l F .text 00000014 .hidden __stack_chk_fail_local
0000b1e7 l F .text 00000000 .hidden __i686.get_pc_thunk.bx
00040e60 l O *ABS* 00000000 .hidden _DYNAMIC
