Some instructions can use >16 bit immediates if they represent a <=16 bit signed value.
However some logical instructions (andi, xori, ori, lui) should always treat the immediate value as unsigned.
This patch adds an ASSERT to these places and a minor change to MacroAssembler::li to satisfy this.

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/9309077
Patch from Daniel Kalmar <kalmard@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10644 ce2b1a6d-e550-0410-aec6-3dcde31c8c00