ARM: Add support for just one string argument in the string add stub

ARM: Add support for just one string argument in the string add stub

Having a string add stub which can handle a string in just one of the arguments is essencial for the type recording binary operation stub when expecting strings. Otherwise string added with e.g. smi will always call the runtime for a type transition which will be back to the same types as the transition code keeps it in string arguments when one argument is a string.

This fixes the regression (especially Delta Blue) caused by replacing the generic binary operation stub with the type recording binary operation stub in the ARM lithium code generator.
Review URL: http://codereview.chromium.org/6551008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6882 ce2b1a6d-e550-0410-aec6-3dcde31c8c00