gconfig refactor

This doesn't fix all the conf_load() issues that future features
need fixed, but it's a good step in the right direction.

rename type to cfg_t
s/extern global_config_t gconfig/extern const cfg_t* gcfg/
extern const global access managed from main.c, not conf.c
conf.c does not operate on the global
global access should fail (NULL ptr deref) if too early
get rid of extern lcmap in libgdnsd
refactor vscf container stacks

... to get rid of signed-vs-unsigned mess and general confusion
make scanner setjmps less likely to clobber

gcc 4.9 newly warns about this situation for this code in the
rfc1035 case, and the fix seems pretty straightforward.  Even
with the old code I haven't observed actual misbehavior, though.
Just better to be safe than sorry if it's warning about the
possibility.  Also updated the djb setjmp code to mirror the
current rfc1035 code.
tiny bugfix: udp_recv_width max should be 64, not 32

It has a correct max of 64 as a global option, but for
some dumb reason was limited to 32 as a per-address option.
refactor dname_isinzone() for clarity

(also, remove nearly-identical code in _isparentof() and reuse)
fixup for gcc/clang warnflags stuff