Reland "Use V8_FINAL and V8_OVERRIDE in various places, fixing bugs revealed by them.".

- Use V8_FINAL and V8_OVERRIDE in Ast classes.
- Use V8_FINAL and V8_OVERRIDE in Lithium mips backend.
- Use V8_FINAL and V8_OVERRIDE in Lithium arm backend.
- Use V8_FINAL and V8_OVERRIDE in Lithium x64 backend.
- Use V8_FINAL and V8_OVERRIDE in Lithium ia32 backend.
- Use V8_FINAL and V8_OVERRIDE in Lithium classes.
- Use V8_FINAL and V8_OVERRIDE in Hydrogen classes.

TBR=dslomov@chromium.org

Review URL: https://codereview.chromium.org/22796020

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16244 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Replace OS::MemCopy with memcpy in typed array initialization.

This is an attempt to fix a weird perf regression on MacOS X 10.6 bot.
Perf regression is not reproducible on MacOS X 10.8.
This difference in memory-copying routines is the only reasonable
difference in the algorithm. We should try and see.

R=bmeurer@chromium.org
BUG=270642

Review URL: https://codereview.chromium.org/23330005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16245 ce2b1a6d-e550-0410-aec6-3dcde31c8c00