style-guide: fix isConst and UnConst examples
style-guide: fix isConst and UnConst examples

Problems:
* missing ; after struct declarations
* missing static for constexpr bool value
* UnConst_<T> -> UnConst_<const T>
* UnConst = -> UnConst = typename

mologie/capnproto,hntrmrrs/capnproto,pjulien/capnproto,pjulien/capnproto,hntrmrrs/capnproto,jparyani/capnproto,mologie/capnproto,jparyani/capnproto,mrdomino/capnproto,hntrmrrs/capnproto,jparyani/capnproto,mologie/capnproto,mrdomino/capnproto,mrdomino/capnproto,pjulien/capnproto