fix `raco exe'
add "share", move "collects" back out of "lib", move "pkgs"

The "share" directory holds platform-independent files, while
"lib" holds platform-specific files.

In principle, the "collects" directory belongs in "share",
as does "doc". Those directories are put into "share"
by a Unix-style install, but left at top level for an
in-place install.

Packages in installation scope are put in "share" instead
of "lib", and the top-level Makefile puts development links
in "share/devel-pkgs".

The `configure' script now supports `--docdir' and `--collectsdir'.

Changed the version to 5.90.0.1.
distro-build: add support for source installers
fix problems with "collects" path and GUI executables
Remove extraneous syntax-class.
Minor optimizer cleanup.
fix "meta/props" for test-file moves
explicit flush after output intended to report progress
Fix typito in INSTALL.txt
Add ffi array-type and in-array
add catalog, source, and Mac OS X instructions to basic README

Also, include "stamp.txt" and "collects.tgz" at a build site.
fix "etc" vs. "config" in `make install' step
raco setup install: add `--source' and `--binary' modes

These flags allow a package downloaded in "built" form to be
stripped to source or binary form, which allows a single catalog
to serve three kinds of installations.
distro-build: change `#:source?' config to mean source packages, too

Use `#:source-runtime?' to make only the run-time system have
source form, while packages are pre-built.
r6rs: fix `(fl+)' and `(fl*)'

Closes PR 13922
fix `arithmetic-shift' with shifts close to `(- (expt 2 31))' on 64-bit

The bug was caused by an accidental cast of a 64-bit integer to a
32-bit integer.

Closes PR 13923
JIT repair for `(/ (most-negative-fixnum) -1)'

When I added JIT-inling of '/' for fixnums, I somehow forgot to
handle the special case that is already handled for `quotient'.
r6rs: fix `div' and `mod'

Closes PR 13925
remove file that has been moved/replaced
fix HtDP language tests