Rename intel to x86.

x86 is the more accurate name, as there are non-Intel x86 implementations.

Fixes #263.

cranelift/filetests/isa/x86/abi-bool.cton

@@ -0,0 +1,20 @@
+test compile
+set is_64bit=1
+isa x86 haswell
+
+function %foo(i64, i64, i64, i32) -> b1 system_v {
+ebb3(v0: i64, v1: i64, v2: i64, v3: i32):
+    v5 = icmp ne v2, v2
+    v8 = iconst.i64 0
+    jump ebb2(v8, v3, v5)
+
+ebb2(v10: i64, v30: i32, v37: b1):
+    v18 = load.i32 notrap aligned v2
+    v27 = iadd.i64 v10, v10
+    v31 = icmp eq v30, v30
+    brz v31, ebb2(v27, v30, v37)
+    jump ebb0(v37)
+
+ebb0(v35: b1):
+    return v35
+}