[System.Data] Remove some win32-specific p/invokes for the mobile profile

[System.Data] Remove some win32-specific p/invokes for the mobile profile

This reduce the size of System.dll and also removes some Win32 specific
p/invokes.

They cause native linking issues for tvOS as Xcode 7.1 does not allow
`-u` in bitcode-enabled builds so we have to call directly the symbols
and it must exists at (native) link time.

**Incomplete** (some remains) but enough so we can run LinkSDK and
System.Data unit tests apps (the managed linker can remove the rest)