link with pthread explicitly

configure.in

@@ -1,7 +1,7 @@
 AC_INIT(configure.in)
 
 AM_CONFIG_HEADER(config.h)
-AM_INIT_AUTOMAKE(ncmpcpp, 0.2.4)
+AM_INIT_AUTOMAKE(ncmpcpp, 0.2.5_pre)
 
 AC_PREREQ(2.59)
 
@@ -34,10 +34,12 @@ else
 fi
 AC_CHECK_HEADERS([ncurses.h], , AC_MSG_ERROR([missing ncurses.h header]))
 
-dnl =====================
-dnl = checking for curl =
-dnl =====================
+dnl =================================
+dnl = checking for curl and pthread =
+dnl =================================
 if test "$curl" = "yes" ; then
+	AC_CHECK_LIB(pthread, pthread_create, LDFLAGS="$LDFLAGS -pthread", AC_MSG_ERROR([pthread library is required]))
+	AC_CHECK_HEADERS([pthread.h], , AC_MSG_ERROR([missing pthread.h header]))
 	AC_PATH_PROG(CURL_CONFIG, curl-config)
 	if test "$CURL_CONFIG" != "" ; then
 		CPPFLAGS="$CPPFLAGS `$CURL_CONFIG --cflags`"