Minor Documentation Incompleteness

[Ronald F. Guilmette]

Just wanted to drop you all a note and say that I was reading the
GNU Make manual online recently, and in the section describing the
$(wildcard pattern) function the significance of asterisks was explained,
but not the significance of other shell-style filename expansion
notations, such as [], which I satisfyingly found also work well
when used in GNU Makefiles.

Maybe you just want to add a bit more into the manual to cover this.