Fix MS-Windows build with libjit

Fix MS-Windows build with libjit

This fixes 32-bit MS-Windows build and hopefully also 64-bit
MS-Windows build (not tested).  32-bit MS-Windows build with wide ints
still doesn't work: I get invalid Lisp objects after JIT compiled code
is invoked.
* configure.ac (HAVE_LIBJIT) [mingw32]: Remove -ljit from
LIBJIT_LIBS, to avoid linking against libjit at build time and
allow loading libjit dynamically at run time.

* src/jit.c [WINDOWSNT]: Include w32.h and w32common.h.
[WINDOWSNT] (DEF_DLL_VAR, LOAD_DLL_VAR): New macros.
(init_libjit_functions) [WINDOWSNT]: New function.
(CONSTANT): A separate version for builds where EMACS_INT_MAX
is equal to INT_MAX (32-bit builds without wide ints).  Use
XLI when assigning Lisp objects to integer values.
(untag, compile_make_natnum, compile_make_number)
(unary_intmath): Handle the case of EMACS_INT_MAX > LONG_MAX.
(compile_current_thread, compile): Don't use CONSTANT for
anything that is not a Lisp object.
(emacs_jit_compile): Do nothing if jit-disable is non-nil.
Use XLP to assign and compare Lisp objects to pointers.
(syms_of_jit): New boolean variable jit-disable, by default nil.
(init_jit) [WINDOWSNT]: Call init_libjit_functions.
Define lisp_object_type separately for 64-bit Windows builds
and 32-bit builds with wide ints.  Fix some signatures to use
lisp_object_type and correct some that deviated from the
actual functions.
* src/lisp.h (USE_STACK_LISP_OBJECTS): Define to false for
32-bit MinGW builds with libjit.
* src/w32fns.c (syms_of_w32fns) <libjit>: New symbol.
* src/eval.c (Ffuncall, funcall_lambda): Use XLP to compare
Lisp_Object vs a pointer.
* src/emacs.c (main): Move the call to init_jit to before
init_buffer, as the latter calls Lisp and could use JIT.
* src/alloc.c (Fmake_byte_code): Use XPL to assign pointer to
a Lisp_Object field.

* lisp/term/w32-win.el (dynamic-library-alist): Add libjit-0.dll.