[vala] (10 commits) ...Use ErrorType-based collection for CodeNode.get_error_types()

[Rico Tzschichholz <ricotz src gnome org>]

Summary of changes:

  28ef85c... tests: Add more invalid "(un)lock" tests to increase covera (*)
  dadfb89... tests: Add invalid "unary decrement" test to increase cover (*)
  ca457c1... vala: Replace and drop UnaryExpression.find_member_access() (*)
  eae660f... tests: Add "no error type in catch" tests to increase cover (*)
  d622c77... vala: Report error for non ErrorType in throws (*)
  9bd5dce... codegen: Use ErrorType.error_domain if possible (*)
  876ace8... parser: Make sure ErrorCodes are accessible as needed (*)
  0a53d37... vala: Implement CodeWriter.visit_foreach_statement() (*)
  d1232b9... vala: Improve CodeWriter.visit_catch_clause() (*)
  0751a9e... Use ErrorType-based collection for CodeNode.get_error_types (*)

(*) This commit already existed in another branch; no separate mail sent