Analyzing RA location on the stack

[Marek Surovič]

The current approach to analyzing the stack frame in RemillStackRecovery can be supplemented by analyzing the location of the return address of the caller relative to the top of the stack stored in the stack pointer. A thing to note is that this needs the ABI to define that the callee is responsible for cleaning up stack.

This kind of analysis could provide information about the number of stack parameters passed into the callee without the callee actually accessing any of the parameters. Which is useful when analyzing callsites of the callee so that we won't recover too many or few parameters.