As libtool suggest we do; this also allows using ACLOCAL_AMFLAGS inside
build that create a separate environment with their own m4 macros, like
jhbuild and Cerberus.
In order to avoid a warning from autoreconf, we create the empty macros
directory during the autogen.sh step; aclocal would create the directory
for us anyway, but different versions of autotools may have different
behaviours.
Closes: #58
Most of the changes that happened after commit 8bbc0d40 broke epoxy
pretty much irreparably because of the CMake build and the attempt at
making libepoxy a static library that can be copy-pasted into another
project without generating files.
Since all the commits are entangled, and are full of unrelated changes,
we cannot simply do a localized set of reverts; instead, we need to hit
the reset button.
From this point forward, we're going to improve libepoxy's build while
attempting to keep the existing build system working. This may mean
reinstating the CMake build system at a later date.
If the '--force' switch is not passed to autoreconf, the autotools will
try to reuse the generated files committed in the Git repo, which hard
code the names and versions of the tools originally used to generate
them.