* module/system/vm/assembler.scm (<meta>, <arity>): Assembler now tracks
arities of a function.
(begin-standard-arity, begin-opt-arity, begin-kw-arity, end-arity):
New macro-assemblers.
* test-suite/tests/rtl.test: Adapt all tests to use begin-standard-arity
and end-arity.
* module/system/vm/assembler.scm (pack-flags): New helper.
(standard-prelude, opt-prelude, kw-prelude): New macro-instructions.
* test-suite/tests/rtl.test: Update tests to use standard-prelude.
* module/system/vm/assembler.scm (assert-match): New helper macro to
check argument types.
(<meta>): Add properties field. Rename name field to "label" to
indicate that it should be unique.
(make-meta, meta-name): New helpers.
(begin-program): Take additional properties argument.
(emit-init-constants): Adapt to begin-program change.
(link-symtab): Allow for anonymous procedures.
* test-suite/tests/rtl.test: Adapt tests.
* module/Makefile.am:
* module/system/vm/assembler.scm: New module, implementing an assembler
for RTL.
* test-suite/Makefile.am:
* test-suite/tests/rtl.test: New test suite.
* module/system/vm/elf.scm (make-elf-symbol*): Add constructor; export
as make-elf-symbol.
(elf-symbol-len): New export.
(write-elf32-symbol, write-elf64-symbol): New helpers.
(write-elf-symbol): New export.
