Move CPU-specific constants from debug.h into the platform-specific directori...

Move CPU-specific constants from debug.h into the platform-specific directories.

The constant for the return sequence length (JSReturnSequenceLength) was
defined in debug.h. Since this constant are also needed outside the debugger code
I moved them into assembler-xxx.h. Otherwise compiling with debuggersupport=off
would fail on ARM.

BUG=http://code.google.com/p/v8/issues/detail?id=533


Committed: http://code.google.com/p/v8/source/detail?r=3383

[Søren Thygesen Gjesse, 2009-11-30 14:59:36]

LGTM, except I am wondering whether the constants should go into CodeGen instead
of Assembler as they are related to how we generate core and not to the
assembler as such.