bug#17715: [PATCH] dfa: build struct dfamust on demand

[Paul Eggert]

Thanks for looking into this.

One little thing I noticed while reading that patch.  dfaalloc could be declared 
with _GL_ATTRIBUTE_MALLOC; this is true both before and after the patch is 
applied.  I don't know if it's worth bothering to declaring it that way, though, 
as I doubt it'd improve the quality of the generated code.  Plus, 
_GL_ATTRIBUTE_MALLOC isn't visible in dfa.h now.