Processing of source should end after END instruction

[michalbali256]

Describe the bug
In HLASM, a program with two END instructions is valid, since the assembler ends processing after encountering the first END. However, that is not the case with this extension.

The problem is most visible when the DB2 preprocessor is enabled - two END instructions are processed by the preprocessor, generating the same symbols twice.

To Reproduce
Steps to reproduce the behavior:
Configure your processor group with the DB2 preprocessor, then type in the following:

   END
   END

32 errors apper, but there should be none.

Expected behavior
Processing should end after the first END.

Platform

• Editor: Any
• OS: Any
• Plugin version: 0.13.0