Fix Issue 4483 - foreach over string or wstring, where element type not specified

core.demangle does not support Unicode and iterates over ASCII only.
add unittest for finalization during library unload
finalize objects whose shared library is about to be unloaded
Add types for Linux/MIPS64.

This adds support for Linux/MIPS64 to druntime. It is not yet complete - at least changes to core.thread are missing.
Merge pull request #740 from redstar/mips64

Add types for Linux/MIPS64.
Merge pull request #658 from MartinNowak/finalizeLibrary

[dll] finalize objects whose shared library is about to be unloaded
Merge pull request #712 from lionello/bug4483

Preparation for issue 4483, specifying foreach char iteration type