Created by: yury-khrustalev
Implements #4356. This patch allows to emulate an OS signal with some number from a function invoked by a clean call. The debugger does not yet point to the intended PC, but functionally it works. I re-use existing internal function "os_forge_exception" and expose its part as a new API function "dr_forge_signal".
Please advise how to better test this new function.