Got the (incomplete) svm1 back end to syntax.

Got the (incomplete) svm1 back end to syntax.

* src/compiler/choose-machine.sh: Added a test that produces the correct
directory name (svm) for TARGET_ARCH svm1.

* src/compiler/machines/svm/.gitignore (new): Ignore generated files.

* src/compiler/machines/svm/assembler-compiler.scm: Fixed to produce
non-empty let bodies in the codecs of instructions with zero
arguments, and fewer unreferenced bindings.

* src/compiler/machines/svm/assembler-runtime.scm: Introduced a module
variable, coding-types, to hold the list of <rt-coding-type>s created
by make-rt-coding-type.  The list is thus no longer required as an
argument to many procedures.

Fixed the trap:* procedures to accept trap arguments.  Fixed the
interface to the interrupt test instructions, which are not (no
longer?) traps.

* src/compiler/machines/svm/compile-assembler.scm: Added a temporary
hack to define write-mit-scheme-copyright in January's snapshot.

* src/compiler/machines/svm/compiler.cbf (new): Cribbed from i386.

* src/compiler/machines/svm/compiler.pkg (new): Cribbed from i386.

* src/compiler/machines/svm/compiler.sf (new): Cribbed from i386.
Referring to compiler.pkg's declarations to get the syntax/load
environments right.

* src/compiler/machines/svm/decls.scm (new): Cribbed from i386.
Collect the list of source files from compiler.pkg, not via *.scm
globs.  Punted initialize/syntax-dependencies!, getting the correct
syntax/load environments from compiler.pkg.

* src/compiler/machines/svm/lapgen.scm: Fixed some typos and
unreferenced bindings.