patch 8.1.2127: the indent.c file is a bit big

Problem:    The indent.c file is a bit big.
Solution:   Move C-indent code a a new cindent.c file.  Move other
            indent-related code to indent.c. (Yegappan Lakshmanan,
            closes #5031)
diff --git a/src/Makefile b/src/Makefile
index cae0e5f..f169548 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -1585,6 +1585,7 @@
 	buffer.c \
 	change.c \
 	charset.c \
+	cindent.c \
 	cmdexpand.c \
 	cmdhist.c \
 	crypt.c \
@@ -1725,6 +1726,7 @@
 	objects/change.o \
 	objects/blob.o \
 	objects/blowfish.o \
+	objects/cindent.o \
 	objects/cmdexpand.o \
 	objects/cmdhist.o \
 	objects/crypt.o \
@@ -1878,6 +1880,7 @@
 	buffer.pro \
 	change.pro \
 	charset.pro \
+	cindent.pro \
 	cmdexpand.pro \
 	cmdhist.pro \
 	crypt.pro \
@@ -3081,6 +3084,9 @@
 objects/charset.o: charset.c
 	$(CCC) -o $@ charset.c
 
+objects/cindent.o: cindent.c
+	$(CCC) -o $@ cindent.c
+
 objects/cmdexpand.o: cmdexpand.c
 	$(CCC) -o $@ cmdexpand.c
 
@@ -3621,6 +3627,10 @@
  auto/osdef.h ascii.h keymap.h term.h macros.h option.h beval.h \
  proto/gui_beval.pro structs.h regexp.h gui.h alloc.h ex_cmds.h spell.h \
  proto.h globals.h
+objects/cindent.o: cindent.c vim.h protodef.h auto/config.h feature.h os_unix.h \
+ auto/osdef.h ascii.h keymap.h term.h macros.h option.h beval.h \
+ proto/gui_beval.pro structs.h regexp.h gui.h alloc.h ex_cmds.h spell.h \
+ proto.h globals.h
 objects/cmdexpand.o: cmdexpand.c vim.h protodef.h auto/config.h feature.h os_unix.h \
  auto/osdef.h ascii.h keymap.h term.h macros.h option.h beval.h \
  proto/gui_beval.pro structs.h regexp.h gui.h alloc.h ex_cmds.h spell.h \