Cache full_path in FileSpec
Find files with arbitrary extensions
Find .cfp files using S_find_files
Add information about .cfp file to CFCParcel

Pass a CFCFileSpec to CFCParcel so it knows about the source or include
dir and full path of the .cfp file.
Skip parcel from include dir if already processed

The parcel from the first source or include dir takes precedence.
Skip file from include dir if parcel was already processed

The parcel from the first source or include dir takes precedence.
Skip class from include dir if parcel was already processed

The parcel from the first source or include dir takes precedence.
Search all dirs in @INC for Clownfish headers
Remove OBJ_HEAD from ivars struct

OBJ_HEAD is only needed once at the start of the object.

(This change was originally part of branch 'ivars_fixes', which I
abandoned.)