Fix compiler errors
Add missing ABCAPI declarations
Change global g_pmib to abc::module_impl::sm_ptOnlyInstance

Fix a design flaw in the original design; this allows to have multiple
modules of different types exist at the same time (e.g. dll1_module,
dll2_module, main_exe_module), as it should be.
Enable exporting symbols from abc-testing library
Fix broken ABC_DECLARE_MODULE_IMPL_CLASS() implementation