Improve object clone performance and make compaction proof.

Bug: 11551604
Bug: 8981901

Change-Id: I60646d838dbb51e125303d1a8fe869191aa63e78
Avoid some string allocations.

Also avoid building a string one character at a time.

Change-Id: I3db26226c620a730b95637d5bfc23e2d4715cfb9

Conflicts:
	runtime/dex_file.cc

Change-Id: I3db26226c620a730b95637d5bfc23e2d4715cfb9
Merge "Avoid some string allocations." into kk44
Merge "Improve object clone performance and make compaction proof." into kk44