patch 8.2.1262: src/ex_cmds.c file is too big

Problem:    src/ex_cmds.c file is too big.
Solution:   Move help related code to src/help.c. (Yegappan Lakshmanan,
            closes #6506)
diff --git a/Filelist b/Filelist
index 49b6534..77fabbe 100644
--- a/Filelist
+++ b/Filelist
@@ -68,6 +68,7 @@
 		src/gui_beval.c \
 		src/hardcopy.c \
 		src/hashtab.c \
+		src/help.c \
 		src/highlight.c \
 		src/indent.c \
 		src/insexpand.c \
@@ -240,6 +241,7 @@
 		src/proto/gui_beval.pro \
 		src/proto/hardcopy.pro \
 		src/proto/hashtab.pro \
+		src/proto/help.pro \
 		src/proto/highlight.pro \
 		src/proto/indent.pro \
 		src/proto/insexpand.pro \