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/misc2.c

@@ -771,7 +771,7 @@ copy_option_part(
     return len;
 }
 
-#ifndef HAVE_MEMSET
+#if !defined(HAVE_MEMSET) && !defined(PROTO)
     void *
 vim_memset(void *ptr, int c, size_t size)
 {
@@ -2609,7 +2609,7 @@ free_username(void)
 }
 #endif
 
-#ifndef HAVE_QSORT
+#if !defined(HAVE_QSORT) && !defined(PROTO)
 /*
  * Our own qsort(), for systems that don't have it.
  * It's simple and slow.  From the K&R C book.
@@ -2676,7 +2676,7 @@ qsort(
  *  (history removed, not very interesting.  See the "screen" sources.)
  */
 
-#if !defined(HAVE_SETENV) && !defined(HAVE_PUTENV)
+#if !defined(HAVE_SETENV) && !defined(HAVE_PUTENV) && !defined(PROTO)
 
 #define EXTRASIZE 5		// increment to add to env. size