A recent gettext release (0.25 via Homebrew) installs the M4 macros in a
different location (<prefix>/share/gettext/m4 instead of
<prefix>/share/aclocal). According to the commit messages to avoid "bad
interactions between autoreconf and autopoint". Since we only depend
on gettext for that macro and this move makes it complicated, we can also
just integrate the macro from gnulib directly (which gettext 0.18+ relies
on anyway).
The parts can be accessed with the variables:
PACKAGE_VERSION_MAJOR
PACKAGE_VERSION_MINOR
PACKAGE_VERSION_BUILD
PACKAGE_VERSION_REVIEW
The last part will be empty for regular releases.
The --disable-defaults option disables all plugins that would be
enabled by default. This allows to selectively enable specific plugins
without issues when new default options get added in future releases.
