compiler: implement copy directly

The compiler now implements the copy builtin directly instead of calling sliceCopy.
The length is calculated with the llvm.umax.* intrinsics, and the move is performed by llvm.memmove.*.
Both of these operations are easily understood by LLVM's optimization passes.
The type's alignment is also provided to llvm.memmove.*, which is useful when rewriting the move.

Interp no longer needs to reimplement sliceCopy.
Some edge case handling was implemented by sliceCopy but not llvm.memmove.*/llvm.memcpy.*.
I copied this over, so copies of external slices should work now.
Volatile moves/copies are now run at runtime by interp.

There is a 4-byte size increase due to some confusing length logic in sendUSBPacket.
I will look at sendUSBPacket in a future PR.

interp/testdata/intrinsics.ll

@@ -0,0 +1,52 @@
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64--linux"
+
+@uminResult = global i32 0
+@sminResult = global i32 0
+@umaxResult = global i32 0
+@smaxResult = global i32 0
+
+define void @runtime.initAll() {
+  call void @main.init()
+  ret void
+}
+
+define internal void @main.init() {
+  call void @testUMin()
+  call void @testSMin()
+  call void @testUMax()
+  call void @testSMax()
+  ret void
+}
+
+define internal void @testUMin() {
+  %umin = call i32 @llvm.umin.i32(i32 12, i32 -1)
+  store i32 %umin, ptr @uminResult
+  ret void
+}
+
+declare i32 @llvm.umin.i32(i32, i32)
+
+define internal void @testSMin() {
+  %smin = call i32 @llvm.smin.i32(i32 12, i32 -1)
+  store i32 %smin, ptr @sminResult
+  ret void
+}
+
+declare i32 @llvm.smin.i32(i32, i32)
+
+define internal void @testUMax() {
+  %umax = call i32 @llvm.umax.i32(i32 12, i32 -1)
+  store i32 %umax, ptr @umaxResult
+  ret void
+}
+
+declare i32 @llvm.umax.i32(i32, i32)
+
+define internal void @testSMax() {
+  %smax = call i32 @llvm.smax.i32(i32 12, i32 -1)
+  store i32 %smax, ptr @smaxResult
+  ret void
+}
+
+declare i32 @llvm.smax.i32(i32, i32)