Rename `read-intern-literal' to `datum-intern-literal'.
Interning is needed only in `read-syntax' or `datum->syntax' to
set up the invariants that the bytecode compiler needs for cross-module
optimization. When `read'ing numbers from a data file, meanwhile,
interning slows things down a lot and doesn't seem worthwhile.
original commit: ee775c3cc3088a8de848399b3c1eec97bbc52b89
This change saves a small amount of space in cross-reference files
and some space in loaded cross-reference information.
It also saves work converting strings to mutable on deserialize,
although the performance difference seems negligible.
original commit: b2fade9206590173e4c2e346357ad13150525387
Also, updates some of the mzlib files to point at `racket/*' libraries
rather than to `scheme/*' ones.
original commit: ac26fe75546b5182d78f18c2cd882f0f440849e2
