lib-test: Added test_ostream for testing nonblocking ostreams.

lib-test: Moved test_istream code to its own test-istream.c file.

configure: Removed --enable-header-install. It's now always enabled. There didn't seem to be much point in keeping it optional anymore. They're now more useful than before because shared libraries are also installed. --HG-- branch : HEAD

Tests are now run on "make check". Added initial tests for lib-index. Moved old tests away from tests/ to libraries' individual directories. --HG-- branch : HEAD