Malformed or crafted data in packstream can make our code attempt
to read or write past the allocated buffer and abort, instead of
reporting an error, which has been fixed.
* jk/patch-corrupted-delta-fix:
t5303: use printf to generate delta bases
patch-delta: handle truncated copy parameters
patch-delta: consistently report corruption
patch-delta: fix oob read
t5303: test some corrupt deltas
test-delta: read input into a heap buffer