* Also enhanced reporting error exit reporting through the scons logger to provide
the exception in the compilation report.
* More error exits in scons should do this.
* Hard imports now have a registry and can be expanded by plugins with
additions at compile time.
* Dedicated helper for fixed imports to use less C code for
standard imports.
* Dedicated node for fixed imports added, for use in standalone
mode in the future.
* Dedicated node for builtin imports, so their special handling is not
in the generic import builtin node anymore.
* Plugins now can look ahead to a module such that they can prepare
by e.g. adding hard imports dynamically created for lazy loader
".pyi" files before loading the code.
* The plugin method for modifying the source now gets the filename,
so it doesn't have to reconstruct it, for our new case where we
want to read nearby ".pyi" file.
