... instead, just calculate the value unless it is too big.
Also, this change raises an ArgumentError if it is expected to exceed
16 GB in a 64-bit environment.

(It is possible to calculate it straightforward, but it would likely be
out-of-memory, so I didn't think it would make sense.)

[Feature #20811]

What a "word" is when talking about sizes is confusing because it's a
highly overloaded term. Intel, Microsoft, and GDB are just a few vendors
that have their own definition of what a "word" is. Specs that used the
"wordsize" guard actually were mostly testing for the size of the C
`long` fundamental type, so rename the guard for clarity.

Also, get the size of `long` directly from RbConfig instead of guessing
using Integer#size. Integer#size is not guaranteed to have anything to
do with the `long` type.

[Feature #20205]

As a path toward enabling frozen string literals by default in the future,
this commit introduce "chilled strings". From a user perspective chilled
strings pretend to be frozen, but on the first attempt to mutate them,
they lose their frozen status and emit a warning rather than to raise a
`FrozenError`.

Implementation wise, `rb_compile_option_struct.frozen_string_literal` is
no longer a boolean but a tri-state of `enabled/disabled/unset`.

When code is compiled with frozen string literals neither explictly enabled
or disabled, string literals are compiled with a new `putchilledstring`
instruction. This instruction is identical to `putstring` except it marks
the String with the `STR_CHILLED (FL_USER3)` and `FL_FREEZE` flags.

Chilled strings have the `FL_FREEZE` flag as to minimize the need to check
for chilled strings across the codebase, and to improve compatibility with
C extensions.

Notes:
  - `String#freeze`: clears the chilled flag.
  - `String#-@`: acts as if the string was mutable.
  - `String#+@`: acts as if the string was mutable.
  - `String#clone`: copies the chilled flag.

Co-authored-by: Jean Boussier <byroot@ruby-lang.org>

Followup: https://github.com/ruby/ruby/pull/10017

[Feature #13557]

[Feature #13557]

Setting the backtrace with an array of strings is lossy. The resulting
exception will return nil on `#backtrace_locations`.

By accepting an array of `Backtrace::Location` instance, we can rebuild
a `Backtrace` instance and have a fully functioning Exception.

Co-Authored-By: Étienne Barrié <etienne.barrie@gmail.com>