Print reason for disabling optimization. Kill --trace-bailout flag.

Provided option to disable full DEBUG build on Android.

Introduced global contexts to represent lexical global scope(s).

Fixed rounding in Uint8ClampedArray setter. (issue 2294)

Performance and stability improvements on all platforms.

git-svn-id: http://v8.googlecode.com/svn/trunk@12394 ce2b1a6d-e550-0410-aec6-3dcde31c8c00