Removes a too-early-and-thus-incorrect call to set_pc_mode_in_cpsr() in execute_handler_from_cache() (transfer_from_sig_handler_to_fcache_return() does this for us at the right time).
Removes an incorrect call to dr_set_isa_mode from the cpsr in transfer_from_sig_handler_to_fcache_return(): we want to only set the mode from the target, not the interruption point.
Works around QEMU bugs with signals 63 and 64 by using 62 instead in the linux.signalNNNN tests. This allows adding them to the list of tests that work under QEMU.
Augments the linux.signalNNNN tests to vary whether the main code and the signal handler are arm or thumb, helping to catch and test signal transition issues.
Issue: #4719, #5233 (closed) Fixes #5233 (closed)