Allow gap before first non-Lisp pseudovec member

Problem reported by Keith David Bershatsky in:
https://lists.gnu.org/r/emacs-devel/2019-04/msg00259.html
Solution suggested by Stefan Monnier in:
https://lists.gnu.org/r/emacs-devel/2019-04/msg00282.html
* src/buffer.h (BUFFER_LISP_SIZE): Simplify by using PSEUDOVECSIZE.
(BUFFER_REST_SIZE): Simplify by using VECSIZE and BUFFER_LISP_SIZE.
* src/lisp.h (PSEUDOVECSIZE): Base it on the last Lisp field,
not the first non-Lisp field.  All callers changed.  Callers
without Lisp fields changed to use ALLOCATE_PLAIN_PSEUDOVECTOR.
(ALLOCATE_PLAIN_PSEUDOVECTOR): New macro.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/w32term.c b/src/w32term.c
index 7dbeda7a716..bb1f0bad018 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -3896,7 +3896,7 @@ x_scroll_bar_create (struct window *w, int left, int top, int width, int height,
   HWND hwnd;
   SCROLLINFO si;
   struct scroll_bar *bar
-    = ALLOCATE_PSEUDOVECTOR (struct scroll_bar, top, PVEC_OTHER);
+    = ALLOCATE_PSEUDOVECTOR (struct scroll_bar, w32_widget_high, PVEC_OTHER);
   Lisp_Object barobj;
 
   block_input ();