fix OpenJDK and Android build regression

c2bfba9 introduced a regression such that building against a non-Avian
class library failed due to avian.Cell not being added to the library.
Since avian.Continuations depends on that class, the build broke.
Merge pull request #209 from joshuawarner32/master

fix lzma build
Merge pull request #210 from dicej/cell

fix OpenJDK and Android build regression
implement Unsafe.{get|put}*Volatile
Merge pull request #213 from dicej/unsafe

implement Unsafe.{get|put}*Volatile
use x86_64-w64-mingw32- prefix for tools like dlltool as necessary

This fixes architecture mismatches when cross-compiling.
Merge pull request #214 from dicej/prefix

use x86_64-w64-mingw32- prefix for tools like dlltool