MAKE-SEQUENCE signals correct error for incompletely user-defined sequences

For the following situation:
- result type is a type specifier designating a DEFTYPEd type
- the type expands to a the name of a user-defined sequence class
- not all mandatory sequence protocol methods are define for the
  user-define sequence class
MAKE-SEQUENCE used to signal a SIMPLE-TYPE-ERROR referring to the
unexpanded type specifier, instead of signaling a
SEQUENCE:PROTOCOL-UNIMPLEMENTED error.

Fixes lp#1315846.
SEQUENCE:PROTOCOL-UNIMPLEMENTED references node in SBCL manual