Add SCons build option to control Microsoft Visual C++ link-time code generation

Add an option to the SCons build to control Microsoft Visual C++ link-time code generation.

Turning off Microsoft Visual C++ link-time code generation makes linking on Windows significantly which is convenient during development. There has also been a request from embedders for a way to control this for embedding application which does not use link-time code generation.

The name of the option is msvcltcg and the default value is 'on' to keep the same behaviour as before.

Committed: http://code.google.com/p/v8/source/detail?r=1742

[iposva, 2009-04-17 22:19:58]

Makes sense to me. -ip