Hi,

as we say in German "Nicht documentiert ist nicht gemacht", if
it is not documented, it wasn't done.

So I thought it would be time to document the changes to the various
ways of specifying CONVERT before gcc12 went out of the door, so
here is a patch for that.

If that goes in, I will also write up something for gcc-12/changes.html.

OK for trunk?  Suggestions for improvements?

Best regards

	Thomas

Document changes to CONVERT for -mabi-ieeelongdouble for POWER

gcc/fortran/ChangeLog:

	* gfortran.texi: Mention r16_ieee and r16_ibm.
	* invoke.texi: Likewise.