fix OSCALL_LSEEK when passed negative numbers
Merge pull request #23 from robert-lytton/master

fix OSCALL_LSEEK when passed negative numbers
Update URL in README.rst to reflect move from rlsosborne to xcore
Fixed bug with re-running programs from xgdb

This could be better implemented, but post-run the structure in
reclaimUnreachableFunctions contains null ptrs, which causes
segmentation faults.

There's probably a better solution, but this works for now.