Rearranged headers to reduce duplication and remove local header
references from fko.h.
Removed references to headers that did not need to be explicitly set.
Moved the MAX_PROTO_STR_LEN and MAX_PORT_STR_LEN definitions to the
fko_limits.h file.
Fixed bug where invalid nat_access or command messages were returning
FKO_ERROR_INVALID_SPA_ACCESS_MSG error code instead of the one
appropriate to the message type.
Fixed bad nat_access_msg test in Perl module test suite (caught by new
validation code).
