DllImportAttribute dllName not explicitly specified for bthprops.cpl

[riverar]

Consider the BluetoothAuthenticateDevice API. This function lives in bthprops.cpl. Without an explicit .cpl suffix, callers may fail attempting to append system native .dll, .a, etc. instead.

Propose that all imports that stray from the defaults be generated with explicit dllNames.

// win32metadata 12.0.2.30863

[DllImport("bthprops", ExactSpelling = true)]
[SupportedOSPlatform("windows6.0.6000")]
public unsafe static extern uint BluetoothAuthenticateDevice([Optional][In] HWND hwndParent, [Optional][In] HANDLE hRadio, [In][Out] BLUETOOTH_DEVICE_INFO* pbtbi, [Optional][In][NativeArrayInfo(CountParamIndex = 4)] PWSTR pszPasskey, [In] uint ulPasskeyLength);

Related: microsoft/windows-rs#1255

[kennykerr]

This also makes the printer APIs impossible to use - we need the file extension.

Here's another customer blocked by this issue:
microsoft/windows-rs#1447