patch 8.1.0825: code for autocommands is mixed with file I/O code

Problem:    Code for autocommands is mixed with file I/O code.
Solution:   Move autocommand code to a separate file. (Yegappan Lakshmanan,
            closes #3863)
diff --git a/Filelist b/Filelist
index d3fcba6..1eb9aa2 100644
--- a/Filelist
+++ b/Filelist
@@ -14,6 +14,7 @@
 		src/arabic.c \
 		src/arabic.h \
 		src/ascii.h \
+		src/autocmd.c \
 		src/beval.c \
 		src/beval.h \
 		src/blob.c \
@@ -146,6 +147,7 @@
 		src/proto.h \
 		src/protodef.h \
 		src/proto/arabic.pro \
+		src/proto/autocmd.pro \
 		src/proto/beval.pro \
 		src/proto/blob.pro \
 		src/proto/blowfish.pro \