basicfuncs: Add upper-case and lower-case functions

This adds two new template functions: $(upper-case) and $(lower-case)
which will upper- or lower-case their UTF-8 arguments. Based on code
from Chris Johnson <chris.johnson3@hp.com>

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
basicfuncs: Add a new $(delimit) template function

The $(delimit DELIMITERS NEW-DELIMITER HAYSTACK) template function takes
three arguments, and replaces all the delimiters from DELIMITERS in the
HAYSTACK with the NEW-DELIMITER.

For example, $(delimit x | fooxbar) would result in "foo|bar".

Based on code and ideas from Chris Johnson <chris.johnson3@hp.com>.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>