Added support to run tests in place.

	- ./configure --enable-tests && make
	- kyua test -k tests/xbps/Kyuafile
README: update instructions to run the tests.
Added a "check" target to run the testsuite.
Added a script that sets up env vars and runs the tests in place.
travis: enable running tests by default (v1).
travis: libssl-devel -> libssl-dev
travis: build deps with make -j16
travis: set LD_LIBRARY_PATH.
travis: add /usr/local/bin to PATH and remove useless LD_LIBRARY_PATH.
tests: libxbps/issue20: do not use ln(1) -r; fails with travis-ci.
tests: libxbps/shell: fix tests that use ln(1) -r on travis-ci.
travis: set LDFLAGS to /usr/local/lib for libatf.
travis: also set LDFLAGS in the configure step.
mk/test.mk: use LDFLAGS when linking too.
travis: remove LDFLAGS from env, should be unnecessary.
bin/xbps-rindex/index-add.c: add assertions to make coverity happy (CID 62741)
Merge branch 'master' into coverity_scan