tests: get rid of the 'shell-or-perl' auxiliary script

tests: get rid of the 'shell-or-perl' auxiliary script

It's now easier and faster to simply run the perl ans shell test
scripts directly with the appropriate interpreter and options.

* tests/shell-or-perl: Delete.
* tests/Makefile.am (EXTRA_DIST): Remove it.
(SH_LOG_COMPILER): Re-define to invoke the correct shell.
(PL_LOG_COMPILER): Re-define to invoke the correct perl
interpreter ...
(TESTSUITE_PERL_OPTIONS): ... with the correct options.
(XPL_LOG_COMPILER): Use those options instead of inlining
their expansion.
(LOG_COMPILER): Delete, no longer needed.