I copied over the rmtree function (and other functions needed by this one)

from the postgresql code so we use that instead of issuing system calls
with rm -rf ....

I also eliminated the rm -rf for pg_xlog.

Will later do the same with the other system call to remove files
in pg_replslot/

Makefile

@@ -5,7 +5,7 @@
 HEADERS = $(wildcard *.h)
 
 repmgrd_OBJS = dbutils.o config.o repmgrd.o log.o strutil.o
-repmgr_OBJS = dbutils.o check_dir.o config.o repmgr.o log.o strutil.o
+repmgr_OBJS = dbutils.o check_dir.o config.o repmgr.o log.o strutil.o dirmod.o
 
 DATA = repmgr.sql uninstall_repmgr.sql