lib: add parse-date.y

lib: add parse-date.y

* include/timeutils.h
    Add parse-date API

* lib/parse-date.y - new file
    Lib function that parses a date string into a timespec struct.
    Derived from gnulib-dd7a871 parse-datetime.y with these changes:
            * reduced to a single function API renamed to parse_date()
            * removed gnulib dependencies
            * removed debugging
            * converted to util-linux coding style

* include/cctype.h - new file
    Like ctype.h only hard coded to the 'C' locale.
    Used by lib/parse-date.y.
    Derived from gnulib-dd7a871 c-ctype.h with these changes:
            * removed gnulib dependencies
            * converted to util-linux coding style
            * add requisite util-linux constants

Signed-off-by: J William Piggott <elseifthen@gmx.com>