fix Issue 12979 - Nothrow violation error is hidden by inline assembler

- deprecate using unattributed asm in attributed functions

- add explicit attributes on asm statments (unverified by compiler)

  asm pure nothrow @nogc @trusted {
    //...
  }

- added new CompoundAsmStatement because the parser
  already splits asm blocks into many AsmStatements
wording of error messages
Merge pull request #4033 from MartinNowak/fix12979

fix Issue 12979 - Nothrow violation error is hidden by inline assembler
fix Issue 13574 - incorrect code for assignment to dollar in slice expression
Merge pull request #4045 from 9rnsr/fix13574

Issue 13574 - incorrect code for assignment to dollar in slice expression
add test case for Issue 9449
Merge pull request #4049 from WalterBright/fix9449

add test case for Issue 9449