patch 8.2.1684: "gF" does not use line number after file in Visual mode

Problem:    "gF" does not use line number after file in Visual mode.
Solution:   Look for ":123" after the Visual area. (closes #6952)
diff --git a/src/findfile.c b/src/findfile.c
index 190fc69..4f69c47 100644
--- a/src/findfile.c
+++ b/src/findfile.c
@@ -1934,6 +1934,13 @@
 
 	if (get_visual_text(NULL, &ptr, &len) == FAIL)
 	    return NULL;
+	// Only recognize ":123" here
+	if (file_lnum != NULL && ptr[len] == ':' && isdigit(ptr[len + 1]))
+	{
+	    char_u *p = ptr + len + 1;
+
+	    *file_lnum = getdigits(&p);
+	}
 	return find_file_name_in_path(ptr, len, options,
 						     count, curbuf->b_ffname);
     }