devel/m4 needs fixing for NetBSD-current

[Jeff Rizzo <riz%netbsd.org@localhost>]

Can someone please fix devel/m4 for NetBSD-current?  Over 2800 packages 
were broken in my recent bulk build because of it.

Basically, the definition of fpos_t changed in -current (and hence, 
NetBSD 6, which alpha I would like to release soon), breaking m4's build.

A speedy fix would be greatly appreciated.

+j