Doxyfile.tmpl: exclude ccan

* template/Doxyfile.tmpl (EXCLUDE): exclude ccan.  [ruby-core:62557]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45972 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
configure.in: disable install-capi by default

* configure.in (install-capi): do not install C API documents by
  default.  [ruby-core:62557]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45973 b2dd03c8-39d4-4d8f-98ff-823fe69b080e