Mark C methods as explicit but also remove explicit check in stats.

Given the use of macros and directives to define methods, the explicit
check should not be used to rule out objects in method counts of stats.

Fixes #727

lib/yard/cli/stats.rb

@@ -128,7 +128,7 @@ def stats_for_constants
       # Statistics for methods
       def stats_for_methods
         objs = all_objects.select {|m| m.type == :method }
-        objs.reject! {|m| m.is_alias? || !m.is_explicit? }
+        objs.reject! {|m| m.is_alias? }
         undoc = objs.select {|m| m.docstring.blank? }
         @undoc_list |= undoc if @undoc_list
         output "Methods", objs.size, undoc.size

lib/yard/handlers/c/handler_methods.rb

@@ -55,6 +55,7 @@ def handle_method(scope, var_name, name, func_name, source_file = nil)
           register MethodObject.new(namespace, name, scope) do |obj|
             register_visibility(obj, visibility)
             find_method_body(obj, func_name)
+            obj.explicit = true
             obj.add_tag(Tags::Tag.new(:return, '', 'Boolean')) if name =~ /\?$/
           end
         end