Round decimal division of tuple elements.

When performing tuple division, the floating point representation of
decimal divisors may yield surprising results.  For example, the
following expression

  >> 1.1.1 / 0.1

can return 9.9.9 or 10.10.10 depending on the host platform.

To address such discrepancies, `round(3)` before casting the result of
tuple element division to a `REBINT`; this should improve cross-platform
consistency.
Use R3's rounding implementation instead of round(3).

This should ensure greater portability as `round(3)` was standardised as
part of C99.
Reduce mem/time for boot and tighten up sizes (appears to fix MSVC build)
TO LOGIC! treats all non-none non-false values as true (CC #2055)
Permit SET-WORD! as the argument to COPY and SET in PARSE (CC #2023)
Fix unwind passing of REDUCE

This fixes CureCode issue #1760: "Unwind functions don't propagate from
REDUCE".
Fix unwind passing of WHILE

This fixes CureCode issue #1519: "Unwind functions don't propagate from
WHILE condition block".
Fix unwind passing of set-word! and SET

This fixes CureCode issue #1515: "Unwind values are assignable with
set-word expressions, SET or SET/any".
Fix unwind passing of functions accepting error!

This fixes CureCode issue #1509: "Unwind functions don't propagate when
called in function arg expression that accepts error! values"
Fix unwind passing of APPLY
Fix unwind passing of set-path!
Fix unwind passing of AJOIN
Add comments to point to where unwinds are handled
Minor (cosmetic) adjustment
IF, EITHER, and UNLESS accept all values in then/else slots (CC #2063)
Per @earl, don't add R_ARG4 for IF/ELSE (which we don't like anyway)
Fix unwind passing of functions with 2+ arguments

This is a fixup to 9cb32ac. The original change was only sufficient for
functions taking exactly one argument (such as the `error?` function).

This fixup now correctly handles unwind passing in multi-argument
functions as well (such as `type?` which takes two arguments: one
regular, one refinement):

    >> foo: func [x y] []

    >> foo break 1
    ** Throw error: no loop to break

    >> foo 1 break
    ** Throw error: no loop to break

    >> foo break continue
    ** Throw error: no loop to break

    >> foo continue break
    ** Throw error: no loop to continue

Corresponding tests have been added to the test suite
(rebolsource/rebol-test@87073d4).
Incorporate /ONLY option for suppressing conditional block evaluation.
Merge pull request #157 from hostilefork/streamline-boot

Reduce mem/time for boot (removes binary scrambler which is no longer necessary) and tightens up sizes.
If you use older C compilers, please let us know if this builds okay.
Merge pull request #104 from 0branch/tuple-div-rounding

Round decimal division of tuple elements. This submission fixes the main problem, but there could be a few edge case issues remaining as pointed out by Ladislav.