Switch the order of the FileDescriptor and EnumValueDescriptor
subsections so that EnumDescriptors and EnumValueDescriptors are
described in adjacent sections.

Also manually move table definition earlier and adjust float placement
options so that all the tables appear in section 4.

Section 5 now begins at top of a page, and includes no floats from
section 4, which is desirable.



git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rprotobuf@863 edb9625f-4e0d-4859-8d74-9fd3b1da38cb