Fix PR422.

Fix PR422.
Ouch! Changes in the lazy initialization code caused each incorporated
function to reprocess the entire function on every lookup of a value's
slot number. This caused a horrible slowdown in all functions. This
fix made llvm-dis go from "longer than I care to wait" (minutes) on a large
test case to 0.53 seconds.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@15818 91177308-0d34-0410-b5e6-96231b3b80d8