Makefile: enable THREADED_DELTA_SEARCH on IRIX and IRIX64
Makefile: enable THREADED_DELTA_SEARCH on IRIX and IRIX64

Since commit dcda3614 removed the use of a variable length array from
builtin-pack-objects.c, it is now safe to compile with the threaded delta
search feature enabled.  Formerly, the MIPSpro 7.4.4m compiler warned that
variable length arrays should not be used with pthreads.

Signed-off-by: Brandon Casey <77bc9a9984e6786c5799d7a71768cf023120ef76@nrlssc.navy.mil>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git