Enhance struct Lisp_Subr to hold the alternative "BC_" function.

Also fix a GC bug, where symbols with position were not being disabled.

* src/lisp.h (union Lisp_Function): New type.
(struct Lisp_Subr): Add fields normal_function, BC_function, and next.
(DEFUN): Setup all three function fields to the subr (BC_function is still a
dummy), set field next to NULL.

* src/alloc.c (Fgarbage_collect): Move the binding of
Qsymbols_with_pos_enabled to garbage_collect_1 so that it gets bound when GC
is invoked via garbage_collect.

* src/lread.c (subr_ptr, using_BC_subrs): New static variables.
(Fswitch_to_BC_subrs, Fswitch_to_normal_subrs): New defuns.
(defsubr): Chain new subr to previous using field next and variable subr_ptr.
(init_lread): Initialise subr_ptr to NULL.
(syms_of_lread): Create subrs Sswitch_to_BC_subrs and Sswitch_to_normal_subrs.

* src/pdumper.c (dump_subr): Enhance to dump struct Lisp_Subr's new fields.
Update the expected value of HASH_Lisp_Subr_xxxxxxxxxx.
(dump_vectorlike): Also dump PVEC_SYMBOL_WITH_POSes.
2 jobs for scratch/accurate-warning-pos in 60 minutes and 1 second (queued for 1 second)
Status Job ID Name Coverage
failed #1232


passed #1233


Name Stage Failure
test-all Test The script exceeded the maximum execution time set for the job
  GEN      lisp/isearch-tests.log
ELC lisp/jit-lock-tests.elc
GEN lisp/jit-lock-tests.log
ELC lisp/json-tests.elc
GEN lisp/json-tests.log
ELC lisp/jsonrpc-tests.elc
GEN lisp/jsonrpc-tests.log
Pulling docker image gitlab/gitlab-runner-helper:x86_64-f100a208 ...
ERROR: Job failed: execution took longer than 1h0m0s seconds