Make trickle thread-safe

thread safety is provided by a big global lock with pthread. There is maybe ways to increase lock
granularity but all I was interested in was to have a safe behavior in a threaded environment.

I have modified the configure.in file so
someone could fall back to the non thread-safe version with the configure script option
--disable-threadsafe

I have improved the AC_CHECK_TYPE macro for in_addr_t. As it was, it was causing a compiling
error on my system.

All the other modifs are from the fact that I did use autoconf 1.69. I had to modernize some parts
of the am/in files to make them work with the latest version.

Signed-off-by: Olivier Langlois <olivier@olivierlanglois.net>

Makefile.am

@@ -17,18 +17,18 @@ man_MANS = trickle.1 trickled.8 trickled.conf.5
 
 bin_PROGRAMS = trickle trickled tricklectl
 
-trickle_DEPENDENCIES = @ERRO@ @LIBOBJS@
+trickle_DEPENDENCIES = @ERRO@ $(LIBOBJS)
 trickle_SOURCES = trickle.c util.c getopt.c
-trickle_LDADD = @ERRO@ @LIBOBJS@
+trickle_LDADD = @ERRO@ $(LIBOBJS)
 
 trickled_SOURCES = trickled.c atomicio.c print.c bwstat.c client.c conf.c \
                    util.c cleanup.c getopt.c xdr.c
-trickled_LDADD = @EVENTLIB@ @LIBOBJS@
+trickled_LDADD = @EVENTLIB@ $(LIBOBJS)
 
 tricklectl_SOURCES = tricklectl.c trickledu.c atomicio.c xdr.c
-tricklectl_LDADD = @ERRO@ @LIBOBJS@
+tricklectl_LDADD = @ERRO@ $(LIBOBJS)
 
-AM_CFLAGS += -Wall -Icompat @EVENTINC@
+AM_CFLAGS = -Wall -Icompat @EVENTINC@
 
 overloaddir = $(libdir)
 overload_DATA = libtrickle.so