Shared library support: Where we are at

[rikki cattermole]

While fixing one of the bugs I have discovered that when using MSVC 
linker, shared libraries that have symbols that contain Unicode is 
currently broken.

It is not on our end. This is a hard blocker for our non-english 
speaking users.

It will mean that we have to do something to sanitize those symbol names 
to make them ASCII in nature.

Unfortunately we had an incomplete test case in the testsuite that only 
covered executables.

https://issues.dlang.org/show_bug.cgi?id=23179