This replaces the custom runtime.memcpy and runtime.memmove functions
with calls to LLVM builtins that should hopefully allow LLVM to better
optimize such calls. They will be lowered to regular libc memcpy/memmove
when they can't be optimized away.
When testing this change with some smoke tests, I found that many smoke
tests resulted in slightly larger binary sizes with this commit applied.
I looked into it and it appears that machine.sendUSBPacket was not
inlined before while it is with this commit applied. Additionally, when
I compared all driver smoke tests with -opt=1 I saw that many were
reduced slightly in binary size and none increased in size.
This commit makes sure all Go types can be encoded in the interface type
code, so that Type.Kind() always returns a proper type kind for any
non-nil interface.
Package encoding/binary uses reflect and is needed by image/png, but
image/png doesn't actually need the reflect-using parts of
encoding/binary. So stub them out for now to get it to compile.
Thanks to Stephen Solka who wrote the patch.
