tests: add .sh and .pl suffixes to shell and perl tests, respectively

Not only this shrinks the size of the generated Makefile (from > 6300
lines to ~3000), but will allow further simplifications in future
changes.

* tests/Makefile.am (TEST_EXTENSIONS): Add '.sh' and '.pl'.
(PL_LOG_COMPILER, SH_LOG_COMPILER): New, still defined simply to
$(LOG_COMPILER) for the time being.
(TESTS, root_tests): Adjust as described.
* All tests: Rename as described.

tests/split/guard-input.sh

@@ -0,0 +1,33 @@
+#!/bin/sh
+# ensure split doesn't overwrite input with output.
+
+# Copyright (C) 2012 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/init.sh"; path_prepend_ ../src
+print_ver_ split
+
+seq 10 | tee exp-1 > xaa
+ln -s xaa in2
+ln xaa in3
+
+split -C 6 xaa && fail=1
+split -C 6 in2 && fail=1
+split -C 6 in3 && fail=1
+split -C 6 - < xaa && fail=1
+
+compare exp-1 xaa || fail=1
+
+Exit $fail