Support automated ‘make check’ in non-C locale

Support automated ‘make check’ in non-C locale

This lets the builder optionally test Emacs behavior in other locales.
The C locale is still the default for tests.
* test/automated/Makefile.in (TEST_LOCALE): New macro.
(emacs): Use it.
* test/automated/flymake-tests.el (flymake-tests--current-face):
Use C locale for subprocesses so that tests behave as expected.
* test/automated/python-tests.el:
(python-shell-prompt-validate-regexps-1)
(python-shell-prompt-validate-regexps-2)
(python-shell-prompt-validate-regexps-3)
(python-shell-prompt-validate-regexps-4)
(python-shell-prompt-validate-regexps-5)
(python-shell-prompt-validate-regexps-6)
(python-shell-prompt-set-calculated-regexps-1):
Adjust expected output to match locale.
* test/automated/tildify-tests.el (tildify-test--test)
(tildify-space-test--test, tildify-space-undo-test--test):
This test assumes UTF-8 encoding.