Improve conformance with usual coding style in effi.c.

Improve conformance with usual coding style in effi.c.

Qabcdef should hold the perfectly normal, interned symbol abcdef, its
C variable should not be named Q_abcdef, that would imply the keyword
:abcdef.

        * effi.c:
        Only declare the symbols corresponding to foreign types if they're
        not declared elsewhere. Follow the usual convention as above.
        * effi.c (FFI_TPTR): Change symbol names here.
        * effi.c (Fffi_basic_type_p): Ditto.
        * effi.c (ffi_canonicalise_type): Ditto.
        * effi.c (Fffi_size_of_type): Ditto.
        * effi.c (Fmake_ffi_object): Ditto.
        * effi.c (Fffi_make_pointer): Ditto.
        * effi.c (Fffi_load_library): Ditto.
        * effi.c (ffi_type_align): Ditto.
        * effi.c (ffi_fetch_foreign): Ditto.
        * effi.c (Fffi_fetch): Ditto.
        * effi.c (Fffi_aref): Ditto.
        * effi.c (Fffi_store): Ditto.
        * effi.c (Fffi_aset): Ditto.
        * effi.c (Fffi_address_of): Ditto.
        * effi.c (Fffi_lisp_object_to_pointer): Ditto.
        * effi.c (extffi_setup_argument): Ditto.
        * effi.c (Fx_device_display): Ditto.
        * effi.c (ffi_callback_call_x86): Ditto.
        * effi.c (Fffi_make_callback): Ditto.
        * effi.c (syms_of_ffi): Use DEFSYMBOL where appropriate, document an
        oddity with Qffiobjectp.
        * general-slots.h: Move Qshort, Qvoid here.
        * lisp.h: Remove Qshort, Qvoid from here.
        * map.c: Ditto.
        * map.c (map_LTX_init): Ditto.
        * mule/file-coding.c: Ditto.
        * mule/file-coding.c (syms_of_file_coding): Ditto.
        * mule/file-coding.h: Ditto.

Signed-off-by: Aidan Kehoe <kehoea@parhasard.net>
Signed-off-by: Steve Youngs <steve@sxemacs.org>