added mingw build support for windows to autotool build

Author: zerotacg

Makefile.am

@@ -302,7 +302,7 @@ libnanomsg_la_SOURCES = \
 pkgconfigdir = $(libdir)/pkgconfig
 pkgconfig_DATA = libnanomsg.pc
 
-libnanomsg_la_LDFLAGS = -version-info @NN_LIBTOOL_VERSION@
+libnanomsg_la_LDFLAGS = -no-undefined -version-info @NN_LIBTOOL_VERSION@
 libnanomsg_la_CFLAGS = -DNN_EXPORTS
 
 ################################################################################

configure.ac

@@ -215,6 +215,7 @@ AS_CASE([${host_os}],
         AC_DEFINE([NN_HAVE_WINDOWS])
         AC_DEFINE([NN_HAVE_MINGW])
         AC_DEFINE([_WIN32_WINNT],0x0600)
+        LIBS="$LIBS -lws2_32 -lMswsock"
     ],
     [*darwin*],  [AC_DEFINE([NN_HAVE_OSX])],
     [*freebsd*], [AC_DEFINE([NN_HAVE_FREEBSD])],