RFC: Rename --enable-intermodule

[Kelley Cook]

I believe that the build option --enable-intermodule is not well named.

If it followed the pattern other GCC build options, it wrongly implies 
that IMA isn't compiled into GCC unless specified.

I propose that it is renamed --enable-build-using-IMA which is generic 
enough that other projects in the tree could use the same option if they 
wish to tweak their makefiles to take advantage of the IMA optimization.

Kelley Cook