Fix generation of package-dependent init names.

The code incorrectly used relative instead of absolute paths to
see if *.babel files could be found, which could result in them
not being located properly.

Also added an underscore between the package and the module name
for package_moduleInit() and package_moduleDatInit() so that there
won't be spurious conflicts, e.g. for package A and module BC vs.
package AB and module C.