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/filetests/filetests/isa/x86/simd-logical-binemit.clif

@@ -25,3 +25,9 @@ ebb0(v0: b64x2 [%xmm6], v1: b64x2 [%xmm3]):
 [-, %xmm3]  v2 = band_not v0, v1      ; bin: 66 0f df de
             return v2
 }
+
+function %x86_ptest_f64x2(f64x2, f64x2) {
+ebb0(v0: f64x2 [%xmm0], v1: f64x2 [%xmm2]):
+[-, %rflags]  v2 = x86_ptest v0, v1      ; bin: 66 0f 38 17 c2
+            return
+}

cranelift/filetests/filetests/isa/x86/simd-logical-legalize.clif

@@ -9,3 +9,11 @@ ebb0(v0: b32x4):
     ; nextln: v1 = bxor v2, v0
     return v1
 }
+
+function %vany_true_b32x4(b32x4) -> b1 {
+ebb0(v0: b32x4):
+    v1 = vany_true v0
+    ; check: v2 = x86_ptest v0, v0
+    ; nextln: v1 = trueif ne v2
+    return v1
+}

cranelift/filetests/filetests/isa/x86/simd-logical-run.clif

@@ -21,3 +21,21 @@ ebb0:
     return v4
 }
 ; run
+
+function %vany_true_i16x8() -> b1 {
+ebb0:
+    v0 = vconst.i16x8 [1 0 0 0 0 0 0 0]
+    v1 = vany_true v0
+    return v1
+}
+; run
+
+function %vany_true_b32x4() -> b1 {
+ebb0:
+    v0 = vconst.b32x4 [false false false false]
+    v1 = vany_true v0
+    v2 = bint.i32 v1
+    v3 = icmp_imm eq v2, 0
+    return v3
+}
+; run