[Xcb] bugfix and cleanups for auto* stuff

[Daniel Martin]

Hi,

these're a few cleanups, mostly for configure.ac and a bugfix for
#66413.


[PATCH 1/6] Initialize automake earlier (bugfix for #66413)

That's the bugfix for:
  libxcb 1.9.1: Fails to build on Arch Linux: \
      /home/<user>/install-sh: No such file or directory
  https://bugs.freedesktop.org/show_bug.cgi?id=66413
It's nearly identical with the suggestion of Alain Kalker, but without
moving the AC_PREREQ.


[PATCH 2/6] Remove second AC_PREREQ, require version 2.60

At the beginning of configure.ac there was a AC_PREREQ(2.57) and later
a second AC_PREREQ([2.59c], ... htmldir ...). The second one was for
backward compatibility, as htmldir was introduced with the testing
release 2.59c. The next stable release (2.60) after 2.59c was released
in June 2006. So, htmldir is in autoconf for more than 7 years, it
should be safe to remove the second AC_PREREQ and bump the requirement
to 2.60.


[PATCH 3/6] Set AC_CONFIG_AUX_DIR to build-aux
[PATCH 4/6] Use build-aux as autom4te cache directory

Use a sepparate directory (build-aux/) for generated/copied files. Due
to that, the project directory doesn't get cluttered that much.


[PATCH 5/6] Use m4 directory

Libtoolize suggests to use AC_CONFIG_MACRO_DIR([m4]) and
ACLOCAL_AMFLAGS. Implement this suggestion and move the libxcb specific
acinclude.m4 as xcb.m4 into that directory.


[PATCH 6/6] Sort gitignore, adjust pattern for config.h

I like to keep things sorted when possible. Additionally, adjust the
pattern for config.h[.in] files to ignore config.in.h~ too.


My knowledge on the whole auto* stuff is very limited. I hope those
changes don't break anything else.


Cheers,
    Daniel Martin

PS: I'm off for some days and may not be able to respond until Tuesday.