patch 8.1.1966: some code in options.c fits better elsewhere

Problem:    Some code in options.c fits better elsewhere.
Solution:   Move functions from options.c to other files. (Yegappan
            Lakshmanan, closes #4889)
diff --git a/src/proto/screen.pro b/src/proto/screen.pro
index 0aaed5f..cf95f79 100644
--- a/src/proto/screen.pro
+++ b/src/proto/screen.pro
@@ -59,7 +59,9 @@
 int redrawing(void);
 int messaging(void);
 void showruler(int always);
+void comp_col(void);
 int number_width(win_T *wp);
 int screen_screencol(void);
 int screen_screenrow(void);
+char *set_chars_option(char_u **varp);
 /* vim: set ft=c : */