Provide TEST_CHAR marco in test_char.h

For (internal) usage outside server/util.c, mod_log_forensic for now
and mod_cache (T_HTTP_TOKEN_STOP) in a few...


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1856490 13f79535-47bb-0310-9956-ffa450edef68