tests: don't skip if $(abs_builddir) or $(abs_srcdir) contain whitespace

tests: don't skip if $(abs_builddir) or $(abs_srcdir) contain whitespace

We used to explicitly skip libtool and gettext tests if the absolute
path of the builddir or of the srcdir which Automake was configured
with contained any whitespace (or other metacharacters).

But several other tests would spuriously fail in such an unholy setup.
To be precise, it would cause 61 'FAIL's and 42 'ERROR's in the whole
Automake testsuite.

The fact that, as of today, nobody has reported any failure of this kind
means that (thankfully) nobody is building automake with $(abs_srcdir)
or $(abs_builddir) mangled by whitespace.  So, instead of trying to cater
to such a broken setup consistently, we just drop the extra check in the
libtool/gettext tests.

In case someone will ever reports a failure due to extra whitespace in
either $(abs_srcdir) or or $(abs_builddir), we will simply enhance our
'configure.ac' to bail out flatly and loudly at such a setup.

* t/ax/test-init.sh: Simplify accordingly.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>