add CDouble/CFloat instances for Element
FFI helpers
improve haddocks for flatten
add Data.Packed.Foreign
use an inline unsafePerformIO
explicit exports, fix argument order of appMatrixRaw
Revert "add CDouble/CFloat instances for Element"

This reverts commit d302e91710db7cccb32853cfd861b9f869eb4e31.
Merge pull request #43 from mikeplus64/master

Add FFI helpers