add more checks

Signed-off-by: Cristian Stoica <crististm@gmail.com>
add support for automake c11 detection

Signed-off-by: Cristian Stoica <crististm@gmail.com>
this is recommended by AX_PTHREAD - need review

Signed-off-by: Cristian Stoica <crististm@gmail.com>
the comprehensive cxx11 check is this one

Signed-off-by: Cristian Stoica <crististm@gmail.com>
update autoconf files - works with gcc3.4, 4.5, 4.7