patch 9.1.1662: Issues with proto files: missing or inconsistent prototypes.

Problem:  Issues with proto files: missing or inconsistent prototypes.
Solution: Update ifdefs, move typedefs, fix prototype declaration
          (Hirohito Higashi)

This change focuses on fixes and tweaks found while working on #18045 for
the proto/*.pro files.

The following fixes and tweaks have been made:

- Fixed a prototype declaration where the variable name differed from
  the function definition.
- Removed a prototype declaration without a function body.
- Fixed a problem where a prototype declaration was not created for a
  function definition enclosed in a #if directive because it lacked ||
  defined(PROTO).
- Moved typedef struct soundcb_S soundcb_T; from proto/sound.pro to
  vim.h.
- Other small tweaks.

The make proto mechanism remains unchanged.

closes: #18058

Signed-off-by: Hirohito Higashi <h.east.727@gmail.com>
Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/option.c

@@ -4748,7 +4748,7 @@ did_set_winwidth(optset_T *args UNUSED)
     return errmsg;
 }
 
-#ifdef FEAT_WAYLAND_CLIPBOARD
+#if defined(FEAT_WAYLAND_CLIPBOARD) || defined(PROTO)
 /*
  * Process the new 'wlsteal' option value.
  */
@@ -4761,7 +4761,7 @@ did_set_wlsteal(optset_T *args UNUSED)
 }
 #endif
 
-#ifdef FEAT_WAYLAND
+#if defined(FEAT_WAYLAND) || defined(PROTO)
 /*
  * Process the new 'wltimeoutlen' option value.
  */
@@ -8915,7 +8915,7 @@ option_set_callback_func(char_u *optval UNUSED, callback_T *optcb UNUSED)
 #endif
 }
 
-#if defined(FEAT_TABPANEL)
+#if defined(FEAT_TABPANEL) || defined(PROTO)
 /*
  * Process the new 'showtabpanel' option value.
  */