libtextstyle: Add a program for ad-hoc testing.
* libtextstyle/adhoc-tests/README: New file.
* libtextstyle/adhoc-tests/hello.c: New file, based on
libtextstyle/examples/color-hello/hello.c.
* libtextstyle/adhoc-tests/hello-default.css: New file, copied from
libtextstyle/examples/color-hello/hello-default.css.
* libtextstyle/adhoc-tests/Makefile.am: New file.
* libtextstyle/configure.ac (AC_CONFIG_FILES): Add adhoc-tests/Makefile.
* libtextstyle/Makefile.am (SUBDIRS): Add adhoc-tests.
