Missing item from gas/doc/internals.texi

[Ben Elliston]

In internals.texi, there is a ``CPU backend'' node that lists functions
and macros that may be defined in the backend files.  It seems to be
missing ``md_atof'', a function called by the core and defined in many
(probably all) backends.

Other than to guess that it's a version of atof() used in the assembly
process, I'm unsure about the function's precise purpose.  Could someone
else document it?

Ben