This also makes autogen.sh compatible with older versions of autotools +
pkg-config.

This fixes issue #262.

This facilitates the development of C++ extensions to graph-tool.

This revers the dependency to 1.54. This can be done since
boost::coroutines has been made optional.

This causes the test to fail when only static variables are available.

This is essentially because of a Debian bug, where no boost::coroutine
shared libraries are available.