Merged some changes from the 4.2 branch:

Merged some changes from the 4.2 branch:
Describe what happens if you do "find -printf %" (with a single % at
the end of the format).  Added test case for "find -printf %H".  Fixes
for "find -perm" with X.  Better range checking in frcode.c.  Tests
for long initially-identical prefixes in frcode.c and that it
correctly encodes paths with mroe than 2^16 characters in comon in the
prefix.  Also initial spaces.  Added --show-limits to the xargs help
message and manpage.