[DynInst_API:] commit: further 9.1.x fixes

[Bill Williams <bill@xxxxxxxxxxx>]

Cleaned up a few things reported by Josh Stone:

* Version #defines in stackwalker and dyninst headers updated for 9.1
* Compile warnings fixed
* BPatch_object::findFunction correctly reports failure/error if the 
function is not found in the BPatch_object, not for each module that 
doesn't contain the function
* BPatch library load/unload callbacks now receive a BPatch_object so 
that they continue to be called once per library, not once per .o within 
a library
* READMEs updated
* Some test suite updates to correspond to the above fixes

--bw