build-sys: fix ENABLE_ALL

Signed-off-by: Karel Zak <kzak@redhat.com>
build-sys: add --enable-pylibmount

 * globally disable all Python bindings by --without-python
 * use --with-python=<version> to specify Python version
 * --enable-pylibmount to override --disable-all-programs

Reported-by: Ruediger Meier <sweet_f_a@gmx.de>
Signed-off-by: Karel Zak <kzak@redhat.com>
build-sys: fix with_python usage, improve logic

We have to set the default withval= on the default with_python=check
otherwise uninitialized value is used.

Signed-off-by: Karel Zak <kzak@redhat.com>
Merge branch 'misc-build-sys' of https://github.com/rudimeier/util-linux

* 'misc-build-sys' of https://github.com/rudimeier/util-linux:
  tests: fix python tests for dist and out-of-tree builds
  build-sys: fix update-potfiles script
  build-sys: restore make distcheck's configure flags
  build-sys: use automake's PYTHON primary for __init__.py
  tests: ignore deprecated last
  tests: remove deprecated mount tests

Conflicts:
	Makefile.am
travis-ci: refactor and add .travis-functions.sh

Travis yaml syntax, where we can only use shell one-liners, is awful
and ugly. We add a real shell script and source it from .travis.yml.

This commit squashes a lot changings because we don't want to
pullote history with this meta CI stuff.

Highlights:
  - enable make distcheck
  - cleanup configure options (enable all progs, with python and docs)
  - shorter config.log dump
  - out-of-tree build supported
  - testing locally is possible now
  - easy to add temporary debugging stuff

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>
travis-ci: workaround broken pylibmount relink

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>