tests: cd to testdir before running so user can do simply '$ tests/run_tests.py'

git-svn-id: https://svn.code.sf.net/p/apertium/svn/trunk/lttoolbox@49997 72bbbca6-d526-0410-a7d9-f06f51895060
lt-print: let show() be const, do joinFinals() in main() instead

git-svn-id: https://svn.code.sf.net/p/apertium/svn/trunk/lttoolbox@50074 72bbbca6-d526-0410-a7d9-f06f51895060
merge master