Fix 'FindCapnProto.cmake' for CMake versions <2.8.12.
Fix 'FindCapnProto.cmake' for CMake versions <2.8.12.

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