-z bndplt documentation in GCC manual

[Sandra Loosemore]

I think the documentation relating to '-z bndplt' in the GCC manual 
description of -fcheck-pointer-bounds is incorrect.  It looks like, as 
of r225862, the GCC driver is supposed to emit an error message if GCC 
was configured with a linker that doesn't support this option and you 
pass -mmpx without -static.  Is that right?  I'll fix the documentation 
once I'm clear on what the actual behavior is.

-Sandra