patch 8.2.0256: time and timer related code is spread out

Problem:    Time and timer related code is spread out.
Solution:   Move time and timer related code to a new file. (Yegappan
            Lakshmanan, closes #5604)
diff --git a/Filelist b/Filelist
index 91e6b04..41eb53f 100644
--- a/Filelist
+++ b/Filelist
@@ -127,6 +127,7 @@
 		src/termlib.c \
 		src/testing.c \
 		src/textprop.c \
+		src/time.c \
 		src/ui.c \
 		src/undo.c \
 		src/usercmd.c \
@@ -275,6 +276,7 @@
 		src/proto/termlib.pro \
 		src/proto/testing.pro \
 		src/proto/textprop.pro \
+		src/proto/time.pro \
 		src/proto/ui.pro \
 		src/proto/undo.pro \
 		src/proto/usercmd.pro \