Bug in wimp.h

[Chris Rutter]

The declaration for wimp_load_template() includes the 12-byte buffer
being `const': this is incorrect, as the Wimp replaces wildcarded names
by the actual name of the template; PRM 3-171 states:

    As the wildcarded name is overwritten by the actual one found,
    it must be re-initialised before every call and must be big
    enough to have the template name written into it.

Furthermore, shouldn't there be a macro for `((wimp_window *) 0xffffffffu)'
(the value to pass to wimp_load_template() if you want to look up the
sizes of the various buffers)?

c.