[perl #117265] TODO tests for overloading issues
[perl #117265] correctly handle overloaded strings
[perl #117265] do most glob \0 checks in the same place

and before we do much processing
[perl #117265] move the "glob failed" warning to the point of failure

This avoids an extraneous warning when globbing fails for other reasons.
[perl #117265] fix various problems with safesyscalls

- handling "" overloading correctly
- avoid an extraneous warning from glob()