remove code for pthread from configure.ac, not used

configure.ac

@@ -20,13 +20,6 @@ if test "x$ac_cv_prog_cc_c99" = xno; then
 fi
 AC_PROG_CPP
 
-# XXX: pthread only if we need mutex or etc.
-AX_PTHREAD(,[AC_MSG_ERROR([Could not configure pthreads support])])
-
-LIBS="$PTHREAD_LIBS $LIBS"
-CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
-CC="$PTHREAD_CC"
-
 AC_PROG_INSTALL
 AC_PROG_LIBTOOL
 AC_PROG_MAKE_SET
@@ -44,7 +37,6 @@ AC_HEADER_STDC
 AC_CHECK_HEADERS([sys/types.h])
 AC_CHECK_HEADERS([errno.h])
 AC_CHECK_HEADERS([stdint.h])
-AC_CHECK_HEADERS([pthread.h])
 AC_CHECK_HEADERS([stdbool.h])
 AC_CHECK_HEADERS([unistd.h])