Update: Improvements to file processing code.

Update: Improvements to file processing code.

Code cleanups.

Add initializer to F_file_mode_t.

Have file closures set id to -1 even on error due to documented design of the close() function.

Provide path type for process path related file system operation failures.
Some operations do not distinguish file or directory but instead only operate on the path itself.
In these cases, the path type is now available for use.

Add F_file_found_not to standard error printer.
This allows for the standard error printer to still report the problem rather than a code.
Using the file-specific standard error printer is still the recommended approach.