support E46

	function! s:fo(a)
		let a:a = 1
	endfunction
since does not support "return" sentence yet,
vimlint outputs an error message for the following code

```vim
function! s:d()
    if 1
        let e = 2
    else
        return 0
    endif
    echo e
endfunction
```
support E133
unreachable code. only in _body()

NG
  if 1
    return 1
  else
    return 2
  endif
  echo 1
support #6
backup
support "variable may not be initialized on some execution path" in _if
support E586, E587, but not used
support "variable may not be initialized on some execution path" in
_for, _while
support "variable may not be initialized on some execution path" in _try
refactoring(): added s:push_varstack()
fixed bug in restore_varstack()
refactoring(): call simpl_varstack() in restore_varstack()
refactoring(): upd debug messages
fixed bug in restore_varstack()
fixed bug in compile_body: invalid "unreachable code"
fixed bug in _try
fixed bug in _try
fixed bug in _try
fixed bug in _try