There is no real need in FuncDeclaration::labmap
Remove VarDeclaration::aggrIndex
Move debugVariable and debugFunc from VarDeclaration to IrVar
FuncDeclaration::inlineAsm is not used
Also move nakedUse from VarDeclaration to IrGlobal
Make FuncDeclaration::isIntrinsic and FuncDeclaration::isVaIntrinsic free functions
Move irFty fields to backend ir classes
Rename Type::irtype to ctype for consistency with dmd and gdc
Remove old unused declarations