#1 Patch: Catch the line number where assertCss was called.

[Mark Hung]

Calling CPPUNIT_ASSERT inside assertCss hides the real line number
where assertCss is called. This patch replace CPPUNIT_ASSERT inside
assesrtCss with std::runtime_error(), rename assertCss to checkCss,
and replace assertCss(...) to CPPUNIT_ASSERT_NO_THROW(checkCss(...))
so developers can catch the failed line number easily.

[Mark Hung]

Update patch to define CPPUNIT_ASSERT_CSS macro instead of throw exception.

[David Tardon]

The final patch is different, but the problem is fixed.