Bigloo: Implement error and exceptions

[okuoku]

Bigloo: Has with-exception-handler thus we can implement it with it and a special re-throw exception.

• http://www-sop.inria.fr/indes/fp/Bigloo/manual-chapter15.html
• It lacks guard which is mandated by SRFI-34. Not sure if it is an oversight or intentional. (Since we need R7RS guard, we need roll out our own anyway.)
• Has thread-parameter concept.

Bigloo's error is not compatible with R7RS or R6RS thus we need our own. Unfortunately, Bigloo do not allow internal symbols thus we need anew yuni/error procedure and use it for loaded libraries.