Merge branch 'cross-fasdump-v2'

Merge branch 'cross-fasdump-v2'

- Introduces a portable fasdumper that the compiler can use for
  cross-compiling.

- Adapt the build system to use it.  This form is not final: we
  should really be using GNU configure's build/host/target form.

- Fix up the i386 back end, particularly floating-point stuff.

- Split svm1 into four architectures: svm1-32be, svm1-32le,
  svm1-64be, svm1-64le.  This way you can, e.g., use your x86 laptop
  to cross-build an svm1-32le system to run on an arm32 machine.

- Various minor other fixes for cross-compilation.