Merge remote-tracking branch 'origin/topic/timw/266-namespaces'

Merge adjustments:

- Preserved original `base_type_no_ref` argument type as ::TypeTag
- Removed superfluous #pragma guard around deprecated TableVal ctor
- Clarify NEWS regarding MetaHook{Pre,Post} deprecations
- Simplify some `::zeek::` qualifications to just `zeek::`
- Prefixed FORWARD_DECLARE_NAMESPACED macro with ZEEK_

* origin/topic/timw/266-namespaces:
  Disable some deprecation diagnostics for GCC
  Rename BroType to Type
  Update NEWS
  Review cleanup
  Move Type types to zeek namespace
  Move Flare/Pipe from the bro namespace to zeek::detail
  Move Attr to the zeek::detail namespace
  Move Trigger into the zeek::detail namespace
  Move ID to the zeek::detail namespace
  Move Anon.h into zeek::detail namespace
  Mark all of the aliased classes in plugin/Plugin.h deprecated, and fix all of the plugins that were using them
  Move all of the base plugin classes into the zeek::plugin namespace
  Expr: move all classes into zeek::detail
  Stmt: move Stmt classes into zeek::detail namespace
  Add utility macro for creating namespaced aliases for classes

src/input.h

@@ -22,7 +22,7 @@ extern void add_to_name_list(char* s, char delim, name_list& nl);
 
 extern void begin_RE();
 
-extern void do_atif(Expr* expr);
+extern void do_atif(zeek::detail::Expr* expr);
 extern void do_atifdef(const char* id);
 extern void do_atifndef(const char* id);
 extern void do_atelse();
@@ -41,5 +41,5 @@ extern std::vector<std::string> zeek_script_prefixes;	// -p flag
 extern const char* command_line_policy;	// -e flag
 extern std::vector<std::string> params;
 
-class Stmt;
-extern Stmt* stmts;	// global statements
+ZEEK_FORWARD_DECLARE_NAMESPACED(Stmt, zeek::detail);
+extern zeek::detail::Stmt* stmts;	// global statements