patch 8.1.0976: dosinstall still has buffer overflow problems

Problem:    Dosinstall still has buffer overflow problems.
Solution:   Adjust  buffer sizes. (Yasuhiro Matsumoto, closes #4002)
diff --git a/src/uninstal.c b/src/uninstal.c
index d0d0b06..7b7e3ef 100644
--- a/src/uninstal.c
+++ b/src/uninstal.c
@@ -60,11 +60,10 @@
  * Returns non-zero when it's found.
  */
     static int
-popup_gvim_path(char *buf)
+popup_gvim_path(char *buf, DWORD bufsize)
 {
     HKEY	key_handle;
     DWORD	value_type;
-    DWORD	bufsize = BUFSIZE;
     int		r;
 
     /* Open the key where the path to gvim.exe is stored. */
@@ -87,11 +86,10 @@
  * Returns non-zero when it's found.
  */
     static int
-openwith_gvim_path(char *buf)
+openwith_gvim_path(char *buf, DWORD bufsize)
 {
     HKEY	key_handle;
     DWORD	value_type;
-    DWORD	bufsize = BUFSIZE;
     int		r;
 
     /* Open the key where the path to gvim.exe is stored. */
@@ -209,7 +207,7 @@
     fd = fopen(path, "r");
     if (fd != NULL)
     {
-	while (fgets(line, BUFSIZE, fd) != NULL)
+	while (fgets(line, sizeof(line), fd) != NULL)
 	{
 	    for (p = line; *p != 0; ++p)
 		/* don't accept "vim60an" when looking for "vim60". */
@@ -335,7 +333,7 @@
 
     printf("This program will remove the following items:\n");
 
-    if (popup_gvim_path(popup_path))
+    if (popup_gvim_path(popup_path, sizeof(popup_path)))
     {
 	printf(" - the \"Edit with Vim\" entry in the popup menu\n");
 	printf("   which uses \"%s\"\n", popup_path);
@@ -349,7 +347,7 @@
 	    remove_openwith();
 	}
     }
-    else if (openwith_gvim_path(popup_path))
+    else if (openwith_gvim_path(popup_path, sizeof(popup_path)))
     {
 	printf(" - the Vim \"Open With...\" entry in the popup menu\n");
 	printf("   which uses \"%s\"\n", popup_path);