Add disjoint syntax object type

* libguile/Makefile.am (libguile_@GUILE_EFFECTIVE_VERSION@_la_SOURCES):
  (DOT_X_FILES, DOT_DOC_FILES, noinst_HEADERS): Add syntax.c and
  syntax.h.
* libguile/evalext.c (scm_self_evaluating_p):
* libguile/goops.c (class_syntax, scm_class_of, scm_goops_early_init):
* libguile/init.c (scm_init_guile):
* libguile/print.c (iprin1):
* libguile/tags.h (scm_tc7_syntax):
* module/oop/goops.scm (<syntax>):
* module/system/base/types.scm (%tc7-syntax, cell->object):
* module/system/vm/disassembler.scm (code-annotation): Wire up the new
  data type.
* libguile/syntax.c:
* libguile/syntax.h: New files.
* module/ice-9/boot-9.scm: Move new definitions to (system syntax
  internal).
* module/system/syntax.scm (print-syntax): New helper.
* module/system/vm/assembler.scm (statically-allocatable?)
  (intern-constant, link-data): Arrange to be able to write syntax
  objects into images.
* module/language/cps/types.scm (&syntax): New type.  Remove
  &hash-table; it was never detected, an internal binding, and we need
  the bit to avoid going into bignum territory.

module/system/vm/disassembler.scm

@@ -210,6 +210,7 @@ address of that offset."
                         ((13) "vector?")
                         ((15) "string?")
                         ((53) "keyword?")
+                        ((#x3d) "syntax?")
                         ((77) "bytevector?")
                         ((95) "bitvector?")
                         (else (number->string tc7)))))