1.0 release plan

[mmastrac]

This is a tracking bug to cover everything we need to do for a 1.0 release:

• 1.0 doc updates #327: doc updates
• ctor/dtor to be made always unsafe in 1.0 #159: make ctor/dtor unsafe, always
• Construction of globals should be punted to a third-party library #161: Construction of globals punted to a 3rd-party library
• Remove syn dependency #124: Remove the dep on syn
• Allow #[ctor] to specify custom link section #321: Allow ctor to specify custom link section

This should be enough to call the library "done", modulo some extra platform support.