TODO:
- update manual
  - document new dynports
  - check signature format markup (dyncall)

- feature: support for function pointers arguments,
    if R closure is passed, auto wrap function a callback object
    the callback object is appended in a global list
- bugfix for using callconv prefixes via dyncall and not dyncall.*.
  using a different callvm for dyncall that may be setup via prefixes and
  resets to default always.
- test R build on solaris and sparc(64).
- document win32 expat binary installation
- callbacks should fail with "not yet implemented" on unsupported platforms
- use raw vectors for 1-to-1 bit encoding of values e.g. raw(8) for (u)int64 values
- handling of Csingle attribute on double vectors
- character encoding support, R supports UTF-8.
- Fortran calling conventions
- dyncall typed pointer
- planed dynports:glut, curl, openal

BUGS:
- OpenBSD 4.8/amd64: SDL failed due to pthread.
  R version on OpenBSD does not provide a shared R library, thus
  the symbols are not resolvable.
  Additional Test for resolving self:
  While dynsym(as.externalptr(NULL), "R_ShowMessage") works on Mac OS X, it fails on OpenBSD.
- demo(ttf) failed on Mac OS X 10.6

