Added raptor_uri_counted_filename_to_uri_string

(raptor_uri_counted_filename_to_uri_string): Added based on
raptor_uri_filename_to_uri_string.  Updated to properly check the
length of the incoming filename and ensure (on unix) that the path
buffer is big enough.  Eliminate strcat() calls while here.

For win32, properly calculate the length when there is a :\ in the
filename.

RAPTOR_FATAL4 added for debugging URI length failures