Tweak preconditions in dynamic.c++.
Tweak preconditions in dynamic.c++.

joliss/capnproto,ocdtrekkie/capnproto,mrdomino/capnproto,vladon/capnproto,jparyani/capnproto-boostpython,MarPiRK/capnproto,pjulien/capnproto,ocdtrekkie/capnproto,khklau/capnproto,geofft/capnproto,jparyani/capnproto-boostpython,kamalmarhubi/capnproto,bryce-gibson/capnproto,joliss/capnproto,zarvox/capnproto,zarvox/capnproto,Fraser999/capnproto,mologie/capnproto,a-richardson/capnproto,maurer/capnproto,khklau/capnproto,geofft/capnproto,pjulien/capnproto,bsn069/capnproto,ligzy/capnproto,nagyistoce/capnproto,geofft/capnproto,modulexcite/capnproto,jparyani/capnproto,bryce-gibson/capnproto,a-richardson/capnproto,rcrowder/capnproto,vladon/capnproto,artillery/capnproto,jparyani/capnproto,jparyani/capnproto-boostpython,hntrmrrs/capnproto,johnkdoe/capnproto,jparyani/capnproto,Fraser999/capnproto,jparyani/capnproto-boostpython,modulexcite/capnproto,a-richardson/capnproto,mologie/capnproto,artillery/capnproto,ocdtrekkie/capnproto,martindale/capnproto,kamalmarhubi/capnproto,zarvox/capnproto,johnkdoe/capnproto,hntrmrrs/capnproto,jparyani/capnproto-boostpython,mrdomino/capnproto,nagyistoce/capnproto,johnkdoe/capnproto,artillery/capnproto,pjulien/capnproto,maurer/capnproto,martindale/capnproto,rcrowder/capnproto,vladon/capnproto,Fraser999/capnproto,nagyistoce/capnproto,martindale/capnproto,bsn069/capnproto,bryce-gibson/capnproto,hntrmrrs/capnproto,bsn069/capnproto,ligzy/capnproto,maurer/capnproto,MarPiRK/capnproto,mologie/capnproto,mrdomino/capnproto,joliss/capnproto,khklau/capnproto,ligzy/capnproto,modulexcite/capnproto,kamalmarhubi/capnproto,rcrowder/capnproto,MarPiRK/capnproto