Export libnftables (again)

This reverts commits d572d59788143945c2a638f12a5227d9b21ce489 and
9f5e49e147219cd161de8cd80cadf8a444969ef0.

Current libnftables API should be stable enough to release it into the
public, and after 4aba100e593f ("rule: reset cache iff there is an
existing cache") we have a simple way to batch commands through this
API.

Suggested-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Makefile.am

@@ -6,3 +6,6 @@ SUBDIRS = 	src	\
 
 EXTRA_DIST =	tests	\
 		files
+
+pkgconfigdir = $(libdir)/pkgconfig
+pkgconfig_DATA = libnftables.pc

configure.ac

@@ -109,6 +109,7 @@ AM_CONDITIONAL([BUILD_XTABLES], [test "x$with_libxtables" == xyes])
 
 AC_CONFIG_FILES([					\
 		Makefile				\
+		libnftables.pc				\
 		src/Makefile				\
 		include/Makefile			\
 		include/nftables/Makefile		\

libnftables.pc.in

@@ -0,0 +1,15 @@
+# libnftables pkg-config file
+
+prefix=@prefix@
+exec_prefix=@exec_prefix@
+libdir=@libdir@
+includedir=@includedir@
+
+Name: libnftables
+Description: Netfilter nf_tables user library
+URL: http://netfilter.org/projects/nftables/
+Version: @VERSION@
+Requires:
+Conflicts:
+Libs: -L${libdir} -lnftables
+Cflags: -I${includedir}

src/.gitignore

@@ -1,4 +1,3 @@
-libnftables.a
 libnftables.la
 parser.c
 parser.h

src/Makefile.am

@@ -24,7 +24,7 @@ AM_YFLAGS = -d
 
 BUILT_SOURCES = parser_bison.h
 
-noinst_LTLIBRARIES = libnftables.la
+lib_LTLIBRARIES = libnftables.la
 
 libnftables_la_SOURCES =			\
 		rule.c				\
@@ -58,7 +58,7 @@ libnftables_la_SOURCES =			\
 		libnftables.c
 
 # yacc and lex generate dirty code
-noinst_LTLIBRARIES += libparser.la
+noinst_LTLIBRARIES = libparser.la
 libparser_la_SOURCES = parser_bison.y scanner.l
 libparser_la_CFLAGS = ${AM_CFLAGS} \
 		      -Wno-missing-prototypes \