update for llvm 3.2
apply jckarter's patch for fixing x86-64 ABI
fix clang's warning about implicit NULL convertion
Implement asExpression and as arguments/operator inc tests
Merge loops in desugarAsOverload
Merge pull request #462 from crabtw/llvm3.2

update for llvm 3.2: master branch
Remove as expression
Merge pull request #461 from agemogolk/as

'as' expression and argument conversions (fix issue #102)
Add primop/pattern 'as' overloads.
Add hasAsExpression default init in Lambda.
Fix unsigned/int comparison warning in codegen.