vim-patch:9.0.1330: handling new value of an option has a long "else if" chain

Problem:    Handling new value of an option has a long "else if" chain.
Solution:   Use a function pointer. (Yegappan Lakshmanan, closes vim/vim#12015)

af93691b53

src/nvim/window.c

@@ -6089,7 +6089,7 @@ static void frame_setwidth(frame_T *curfrp, int width)
 }
 
 // Check 'winminheight' for a valid value and reduce it if needed.
-void did_set_winminheight(void)
+const char *did_set_winminheight(optset_T *args FUNC_ATTR_UNUSED)
 {
   bool first = true;
 
@@ -6106,10 +6106,11 @@ void did_set_winminheight(void)
       first = false;
     }
   }
+  return NULL;
 }
 
 // Check 'winminwidth' for a valid value and reduce it if needed.
-void did_set_winminwidth(void)
+const char *did_set_winminwidth(optset_T *args FUNC_ATTR_UNUSED)
 {
   bool first = true;
 
@@ -6126,6 +6127,7 @@ void did_set_winminwidth(void)
       first = false;
     }
   }
+  return NULL;
 }
 
 /// Status line of dragwin is dragged "offset" lines down (negative is up).