I searched on the open standards website, particularly the C working group homepage but only found information about C11.
They seem to have regular meetings and discuss
A technical corrigendum is issued to correct a technical error or ambiguity. New features and extensions need to be published as an amendment or revision of the standard.
See here for an in depth description of the procedure for developing an international standard: http://isotc.iso.org/livelink/livelink?func=ll&objId=4230452&objAction=browse&sort=subtype