Handle AtomicRMWInst (on i32 only)
Partially implement the IRT's sysconf() interface

Implement the PAGESIZE request since use of newlib's malloc() aborts without it.
Add a stub for the IRT's close() function because newlib calls it on exit
Use ccache to speed up rebuilds, if it is available
Extend arithmetic tests to generate LLVM IR test code as well as C test code
Make all arithmetic operations work for i16 and i8
Add notes about how integer types are represented
Fix BranchInst to ignore undefined bits of the condition value
Handle some binary operators on i1: 'and', 'or', 'xor'