* tests/test_driver.pl: Save error strings for later comparison.
* tests/run_make_tests.pl: Create portable commands for later use.
* tests/*: Use these new variables.
* NEWS: Add information about reading files.
* make.texi (File Function): Describe reading files.
* tests/scripts/functions/file: Test new features for $(file ...)
Reported by Tim Murphy <tnmurphy@gmail.com>
* function.c (func_file): Only write TEXT if it is not NULL.
* NEWS, doc/make.texi: Document the new feature
* tests/scripts/functions/file: Verify that the no-text version of
$(file ...) works and doesn't add a newline.
