patch 8.1.2057: the screen.c file is much too big

Problem:    The screen.c file is much too big.
Solution:   Split it in three parts. (Yegappan Lakshmanan, closes #4943)
diff --git a/Filelist b/Filelist
index d7c6e0f..0a686f3 100644
--- a/Filelist
+++ b/Filelist
@@ -32,6 +32,8 @@
 		src/dict.c \
 		src/diff.c \
 		src/digraph.c \
+		src/drawline.c \
+		src/drawscreen.c \
 		src/edit.c \
 		src/eval.c \
 		src/evalbuffer.c \
@@ -192,6 +194,8 @@
 		src/proto/dict.pro \
 		src/proto/diff.pro \
 		src/proto/digraph.pro \
+		src/proto/drawline.pro \
+		src/proto/drawscreen.pro \
 		src/proto/edit.pro \
 		src/proto/eval.pro \
 		src/proto/evalbuffer.pro \