This patch has to be approved before I can commit it.

It fixes a small glitch in GDB MI. MI2 is a default. So
MI and MI2 should work identically. The MI2 being set as
a default is hard-coded in several places. I think one
place was missed:

    mi/mi-main.c::mi_load_progress().

Without this fix, MI "-target-download" command behaves
differently on MI versus MI2 not showing loading progress,
when "-i=mi2" is used.

GDB front-ends developers might want to stick with "-i=mi"
assuming they always use a default. It would be a bad idea
to force them to use explicit options like "-i=mi2".

-- Maxim