Based on remarks made by Dominik Hirt, I have modified manifest generation so that,

in logback-core's manifest the import declaration for package "org.codehaus.janino" has resolution optional, 
and in logback-classic's manifest file, the import declarations for packages "sun.reflect" and "javax.jms" 
have resolution=optional. Moreover, in logback-classic, org.slf4j.impl is exported as version=1.5.6.

Thus, the logback bundles should be resolvable without any modifications and without requiring any 
springsource bundles for jms and janino. 

Related to LBCLASSIC-101