maint: fix gendocs.sh permissions

* build-aux/gendocs.sh: Restore executable bit.

Signed-off-by: Eric Blake <eblake@redhat.com>
pty: Activate the signature wrapper of forkpty.

The intended preprocessor macro HAVE_FORKPTY is
never defined, yet `lib/forkpty.c' depends on it.

* m4/pty.m4 (gl_FUNC_FORKPTY): At completed analysis,
apply AC_DEFINE_UNQUOTED to HAVE_FORKPTY with value
$HAVE_FORKPTY for access to wrapper in `lib/forkpty.c'.
ignore-value: prefer GCC version back through 2.0

The code didn't match the comments, so I did a bit of software
archaeology.  GCC 2.0 seems to support __extension__ and
__typeof__, so fix both code and comments to use 2.0.
* lib/ignore-value.h (ignore_value): Use __extension__ and
__typeof__ for GCC 2.0 through 3.3, too.
selinux-h: improve stub types and add more stub functions

* lib/se-selinux.in.h: Change security_context_t to a typedef
rather than a define, as it's a pointer type and so is better
as a typedef to avoid issues declaring multiple variables
with the comma operator.  Also add stub for string_to_security_class().
* lib/se-context.in.h: Add stub functions for
context_{type,range,role,user}_get().
ignore-value: revert previous code change

* lib/ignore-value.h (ignore_value): Use __extension__ and
__typeof__ only for GCC 3.4 and later.  Reported by Eric Blake in
<http://lists.gnu.org/archive/html/bug-gnulib/2013-11/msg00102.html>.
Change the comment to try to explain this better.
autoupdate
autoupdate
base64: fix recent compilation regression on some compilers

This fixes a compile failure with
  "Sun C 5.8 Patch 121015-05 2007/08/01"
which returns:
  "base64.c", line 99: void function cannot return value

* lib/base64.c: Don't return the void function,
instead split to a separate return statement.