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).
Enhanced the libfko decoding routine to include bounds checking on decrypted
SPA data. This includes verifying the number of fields within incoming SPA
data (colon separated) along with verifying string lengths of each field.
