Grouped named import

[ryuukk_]

Saw this somewhere, and to be honest, that's something i always 
wanted to be able to do

That may be something i could try to implement, sounds relatively 
easy

```D
import c = sqlite3, miniz;
```

It means, symbols from sqlite3 and miniz are isolated into the c 
name

Example:

```D
c.sqlite3_init();
c.miniz_init();
```

This is useful for ImportC, in case of symbol clashes with libc 
symbols from druntime for example

https://dlang.org/spec/module.html#renamed_imports