Convert the remaining TryCatch statements to use QV4::Exception

v8::Script::Run doesn't catch the exception anymore. Instead we handle
this on the calling side, removing all needs for v8::TryCatch.

Change-Id: I946269a6734f50c728c4f153c00cd19db48f1a6a
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Get rid of v8::TryCatch and v8::Message

They are now unused, so let's remove them from the v8 API.

Change-Id: I9c1b39632cb88785ae6fdda671580e0426ae97ba
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>