Semantics of 'static lifetime are not explained

[ettolrach]

It's never explained what 'static actually means. Currently, the only definition of 'static given is two examples of what could be 'static. Namely:

• "Both constant and static declarations of reference types have implicit 'static lifetimes unless an explicit lifetime is specified."

  reference/src/lifetime-elision.md

  Line 185 in b3ce606

  ## `const` and `static` elision

  
  

  reference/src/items/constant-items.md

  Line 24 in b3ce606

  Constants must be explicitly typed. The type must have a `'static` lifetime: any

• "string literaly always have 'static lifetime."

  reference/src/subtyping.md

  Line 14 in b3ce606

  Consider the following example: string literals always have `'static`

  
  

  reference/src/expressions/literal-expr.md

  Line 176 in b3ce606

  That is, the type is `&'static str`.

The exact semantics of 'static should be made clear.