PPChar type seems to be incorrect for {$MODESWITCH UNICODESTRINGS}
## Summary
When using `{$MODESWITCH UNICODESTRINGS}`, type `PPChar` doesn't work as expected.
## System Information
- **Operating system:** Windows
- **Processor architecture:** x86, x86_64
- **Compiler version:** 3.2.2
- **Device:** Computer
## Steps to reproduce
```plaintext
program test;
{$MODE OBJFPC}
{$MODESWITCH UNICODESTRINGS}
var
S: string;
pS: PChar;
ppS: PPChar;
begin
S := 'test string';
pS := @S[1];
ppS := @pS;
pS := ppS^; // Error: Incompatible types: got "PChar" expected "PWideChar"
WriteLn(string(pS));
end.
```
## What is the current bug behavior?
See above comment line.
## What is the expected (correct) behavior?
With `{$MODESWITCH UNICODESTRINGS}`, `PPChar` should be `^PChar`.
## Possible fixes
Can fix above code by adding:
```plaintext
type
PPChar = ^PChar;
```
issue