compile error with older gcc (e.g., 4.2.1):

In file included from wks-receive.c:30:
mime-parser.h:53: error: redefinition of typedef 'rfc822parse_t'
rfc822parse.h:23: error: previous declaration of 'rfc822parse_t' was here

See also T2824. The resolution could be the same as the one described in
issue 2824 - ignore error due to old compiler.