rust-index: add Sync bound to all relevant mmap-derived values
All readonly mmaps are Sync as far as Rust is concerned. Integrity of the
mmap'ed file is a concern separate to Rust's memory model, since it requires
out-of-program handling via locks, etc.
This will help when we start sharing the Rust Index with Python.
{
// Enforcing
"eqeqeq" : true, // true: Require triple equals (===) for comparison
"forin" : true, // true: Require filtering for..in loops with obj.hasOwnProperty()
"freeze" : true, // true: prohibits overwriting prototypes of native objects such as Array, Date etc.
"nonbsp" : true, // true: Prohibit "non-breaking whitespace" characters.
"undef" : true, // true: Require all non-global variables to be declared (prevents global leaks)
// Environments
"browser" : true // Web Browser (window, document, etc)
}