Get new tests integrated with the build system

Check the makefile.am, and configure.ac.
Do the followings:
1. Edit $root/configure.ac, add : AC_CONFIG_FILES([tests/ntpd/Makefile])
2. Put source codes in $root/tests/ntpd
3. Write or copy a makefile.am from similar directroy(eg.
$root/tests/libntp) to $root/tests/ntpd, and (Edit
$root/tests/makefile.am)
4. swtich to $root/ , run *automake*, then makefile.in will be generated
in $root/tests/ntpd
5. run ./configure in $root dir, This will generate the Makefile
6. run *make check* in $root dir, then your program will be generated.