runtime: avoid malloc during malloc
runtime: avoid malloc during malloc

A fault during malloc might lead to the program's
first call to findfunc, which would in turn call malloc.
Don't do that.

Fixes issue 1777.

R=golang-dev, gri
CC=golang-dev
http://codereview.appspot.com/5689047

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang