Push the return address via an intermediate register on 32-bits

git-svn-id: http://address-sanitizer.googlecode.com/svn/trunk@1959 3c3640eb-14a6-2bb8-0b94-e9e73afe33f5
Only use the base register for R1 if it's down-size'able to a byte

git-svn-id: http://address-sanitizer.googlecode.com/svn/trunk@1960 3c3640eb-14a6-2bb8-0b94-e9e73afe33f5