prologue detection

[Frank Ch. Eigler]

Hi -

While trying to run some measurements on the static instrumentation
code, I came across an amusing and troubling bug in the translator's
prologue-detection heuristic.  For some classes of functions (in this
case, prologue-less ones), it would get it totally wrong, and
designate an instruction within a subsequent block.  I've seen one
case where the probe was placed *beyond* the requested function.  

I'm taking a little detour to try to simplify & fix this part up.  In
the mean time, you may want to double-check the placement of probes in
your scripts, especially when on short funtions.  Please send me
anything suspicious that you may have recently seen.

- FChE