Corrected a variety of wrong-arg-type error messages for map-image,
build-image, et al.

Please merge to release branch.
Merge branch 'master' of pltgit:plt
I'm not sure why this is non-fast-forwardable, but it apparently is.
configure: strip debug symbols on install by default
src/README: improve notes on cross-compilation
android: disable libunwind for now

There's an issue with dl_iterate_phdr().
JIT ARM: improve stack trace

Fix a problem at the boundary of DWARF-driven backtrace
and frame-driver backtrace, as well as handling of the
JIT's different internal calling conventions.

Also, allow crossing back from frame-driven to DWARF-driven.
Add MZ_TRY_EXTFLONUMS to OpenBSD.

Also add an error to unsupported platforms (copied from FreeBSD).

Merge to 5.3.4
Fix types of `system` etc for new keyword arguments.

This requires extending the ->optkey type constructor to support rest
arguments, and fixing the keyword function type generation code.

Testing is still limited because there's no parsing for such types.
That will be handled in a later commit.
ffi/unsafe/obj: add `+A' and `-A' method modes

On Cocoa, a view's `drawRect:' method can be called from a
heartbeat thread that animates controls. Such a call happens
rarely for a `canvas%' or other class where `drawRect:'
is overridden, but since it can happen, ensure that the
callback runs on the Racket thread.
Complain visibly when cannot load GL shared libs, instead of swallowing error.
ffi/unsafe: add `_double' and `_float' tests
upgrade libffi to 3.0.13

This upgrade is particularly for repairs to ARM and the VFP ABI.
fix problem with switchable-button tool tip

Closes PR 12562

Merge to v5.3.4
win64: JIT stack-trace repair

Relevant to PR 13702

Merge to 5.3.4
Extra tests.
pkg/lib: doc correction
pkg/lib: fix `installed-pkg-names'
mrlib/terminal: generalize to allow an embedded terminal

That is, instead of always creating a new frame, allow the terminal
GUI to work as a panel.
scribble/reader: allow escape character to be non-ASCII
raco test: make `-r' and `-x' mutually exclusive.