Include hamcrest-core explicitly in test classpath.

Include hamcrest-core explicitly in test classpath.

Otherwise I get errors like:

    [junit] Testcase: initializationError(nom.tam.fits.test.AsciiTableTest):    Caused an ERROR
    [junit] org/hamcrest/SelfDescribing
    [junit] java.lang.NoClassDefFoundError: org/hamcrest/SelfDescribing

I don't have this problem with my Gentoo ebuid, because (I think)

    ANT_TASKS="ant-junit4" eant

is taking care of the classpath adjustment automatically
(hamcrest-core is listed in /usr/share/junit-4/package.env as a
dependency).