Only test mkl library with --with-libmkl

If we do not make the test conditionally and use --without-libmkl during configure,
we end up with -Lno in LDFLAGS.

Signed-off-by: Justin Lecher <jlec@gentoo.org>
Update logic for mkl location testing

Signed-off-by: Justin Lecher <jlec@gentoo.org>
Merge pull request #18 from jlec/master

Only test mkl library with --with-libmkl
Reverted last change 4e6ca9e257030a4d949735665348e3d02937b5f2 due to unacceptable side effects, and implemented a different approach to try and fix issue #18
Merge branch 'master' of https://github.com/POV-Ray/povray
Add uv-mapping to sphere_sweep