Constructor.
PATH is path name of file (create an empty CArchive if path is None).
START is the seekposition within PATH.
LEN is the length of the CArchive (if 0, then read till EOF).
Add an ENTRY to the CArchive.
ENTRY must have:
entry[0] is name (under which it will be saved).
entry[1] is fullpathname of the file.
entry[2] is a flag for it's storage format (0==uncompressed,
1==compressed, 2==Python source format)
entry[3] is the entry's type code.
Get the contents of an entry.
NAME is an entry name.
Return the tuple (ispkg, contents).
For non-Python resoures, ispkg is meaningless (and 0).
Used by the import mechanism.