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.

compiler/cgen.nim

@@ -1050,6 +1050,7 @@ proc getSomeInitName(m: PSym, suffix: string): PRope =
   assert m.owner.kind == skPackage
   if {sfSystemModule, sfMainModule} * m.flags == {}:
     result = m.owner.name.s.mangle.toRope
+    result.app "_"
   result.app m.name.s
   result.app suffix