Add x86 SIMD vany_true and x86_ptest

In order to implement SIMD's any_true (https://github.com/WebAssembly/simd/blob/master/proposals/simd/SIMD.md#any-lane-true), we must legalize some instruction (I chose `vany_true`) to a sequence of `PTEST` and `SETNZ`. To emit `PTEST` I added the new CLIF instruction `x86_ptest` and used CLIF's `trueif ne` for `SETNZ`.

cranelift/codegen/meta/src/isa/x86/opcodes.rs

@@ -375,6 +375,10 @@ pub static PSUBUSB: [u8; 3] = [0x66, 0x0f, 0xd8];
 /// and saturate results (SSE2).
 pub static PSUBUSW: [u8; 3] = [0x66, 0x0f, 0xd9];
 
+/// Set ZF if xmm2/m128 AND xmm1 result is all 0s; set CF if xmm2/m128 AND NOT xmm1 result is all
+/// 0s (SSE4.1).
+pub static PTEST: [u8; 4] = [0x66, 0x0f, 0x38, 0x17];
+
 /// Push r{16,32,64}.
 pub static PUSH_REG: [u8; 1] = [0x50];