WIP: Deprecate std.c.* and move all remaining declarations to core.stdc.*

I'm still working on this, thought I'd get the first cut of the low-hanging fruit up on the auto-tester before I move forward with the more involved modules.  Ultimately, it will need to be merged simultaneously as [druntime pull #893](https://github.com/D-Programming-Language/druntime/pull/893).

I used the same process to deprecate `std.c.string` recently.  If anybody sees any problems with the pull so far, please speak up.
Mmm, In win32 and win 64, using `setenv` and `unsetenv` will cause link-failure.

```
OPTLINK (R) for Win32  Release 8.00.15
Copyright (C) Digital Mars 1989-2013  All rights reserved.
http://www.digitalmars.com/ctg/optlink.html
test.obj(test)
 Error 42: Symbol Undefined _setenv
test.obj(test)
 Error 42: Symbol Undefined _unsetenv
--- errorlevel 2
```

```
test.obj : error LNK2019: unresolved external symbol setenv referenced in function _Dmain
test.obj : error LNK2019: unresolved external symbol unsetenv referenced in function _Dmain
test.exe : fatal error LNK1120: 2 unresolved externals
--- errorlevel 1120
```

They are not available now?