come to terms with RARG register != function return register,
so profiling for amd64 will work.  (the thread library notwithstanding.)

Reference: /n/patches.lsub.org/patch/profrarg.1
Date: Wed Sep 19 06:04:48 CES 2012
Signed-off-by: quanstro@quanstro.net

# rm /sys/src/libc/sparc/port/profile.c
# rm /sys/src/libc/sparc/*/main9p.s