handy.h: add _memEQs() and _memNEs() for use with constant strings

handy.h: add _memEQs() and _memNEs() for use with constant strings

memEQs() is already defined, and requires a length parameter for
the first pointer argument. However some times we do not have
this length handy and simply want to use the length of the constant
string instead.

In an ideal world, to be compatible with more s suffix macros,
IMO the existing memEQs() should have been called something like
memEQsl() maybe, and the ones I am adding would get the memEQs(
name, but it didnt work out like that.