Add initial implementation of high-level module import support.

Implemented in Squirrel. Uses builtin dofile(), so works with source/bytecode
modules so far.
Add basic testsuite for high-level import functions.
Add defines to support building both dyna and static module from same source.
Add sample dummy module source.
Add AUTHORS file.
Add README.
Check that interpreter properly propagates script error to rc code.
Add more checks to import testsuite.
Preserve original proof-of-concept import implementation using dofile().
Convert high-level import to use low-level _import_() from binmodule.
Update project name, add copyright.
Declare module init function as extern "C".
Avoid double dynaload API calls and properly report errors during loading.

Both dlopen() and LoadLibrary() check for already loaded modules themselves.
Previosly, error flag was raised, but error message not set, so previously
set error was reported to user.
Add API version to HSQAPI structure and check for mismatch on module init.
Update for sqmodule API change.
Link modules with --no-undefined, or it's easy to get non-loadable ones.

What's even more important, without --no-undefined, non-loadable module
can be produced without any compile or link time warnings.
Add simple test for sample module.
Add initial implementation of ffi module.

Works, but inly the most basic types are supported.
Support returning strings.
Add strdup test.