Val(): incorrect value for Code (error parameter) for unsigned types if input is negative
## Summary
It you use Val() with an unsigned integer type and the inputstring represents a negative number, then Code (the third parameter) does not point to the correct errorposition.
## System Information
N/A
## Steps to reproduce
```pascal
var
U: Word;
Code: Integer;
begin
Val('-1',W,Code);
writeln('Code: ',Code); //outputs: 2
Val('-0x1',U,Code);
writeln('Code: ',Code); //outputs: 4
end.
```
## What is the expected (correct) behavior?
In both cases it should output 1.
## Possible fixes
The code for the unsigned val-helpers start like this:
```pascal
fpc_Val_UInt_Shortstr:=0;
Code:=InitVal(s,negative,base);
If Negative or (Code>length(s)) Then
Exit;
```
If negative Code should be set to Pos('-',S)
If so desired I'll create a patch.
issue