workaround for QC110889 required on XE3 64bit

What steps will reproduce the problem?
1. Compile the project DwsIdeDemo.dpr with Delphi XE3 64bit.
2. Run the program.
3. Execute any script (even a blank script causes the error).

What is the expected output? 
The script should execute.

What do you see instead?
Project DwsIdeDemo.exe raised exception class $C0000005 with message 
'c0000005 ACCESS_VIOLATION'.

What version of the product are you using? On what operating system?
dwscript trunk revision 36618
Windows 7 Ultimate

Please provide any additional information below.
I traced this to function StrDeleteLeft in dwsUtils always returning empty 
string on Delphi XE3 64bit due to QC110889 which has since been fixed in XE4.

See http://qc.embarcadero.com/wc/qcmain.aspx?d=110889 for more info.

For users still on Delphi XE3, it would be useful if you could implement the 
following workaround: always specify all three parameters when calling Copy. In 
function StrDeleteLeft, replace

   Result:=Copy(aStr, n+1);

with

   Result:=Copy(aStr, n+1, Length(aStr)-n);

In function StrAfterChar, replace

      Result:=Copy(aStr, p+1)

with

      Result:=Copy(aStr, p+1, Length(aStr)-p)

Also affected: TStrSplitFunc.DoEvalAsVariant in dwsStringFunctions.

Original issue reported on code.google.com by bogdan...@gmail.com on 5 Oct 2014 at 9:32

ghkweon / dwscript

workaround for QC110889 required on XE3 64bit #491