libosip2: disable multi-thread support for toolchains without threads

Also added license information

Fixes:
http://autobuild.buildroot.org/results/dcf/dcfbdc1a1ee032881ad5e2f7ca6622d90fc7cb19

[Peter: License is LGPLv2.1+
Signed-off-by: Gilles Talis <gilles.talis@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/libosip2/libosip2.mk

@@ -7,5 +7,10 @@
 LIBOSIP2_VERSION = 3.6.0
 LIBOSIP2_SITE = $(BR2_GNU_MIRROR)/osip
 LIBOSIP2_INSTALL_STAGING = YES
+LIBOSIP2_LICENSE = LGPLv2.1+
+LIBOSIP2_LICENSE_FILES = COPYING
+
+LIBOSIP2_CONF_OPT = \
+	--enable-mt=$(if $(BR2_TOOLCHAIN_HAS_THREADS),yes,no)
 
 $(eval $(autotools-package))