Rename intel to x86.

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

Fixes #263.

cranelift/filetests/isa/x86/legalize-libcall.cton

@@ -0,0 +1,16 @@
+test legalizer
+
+; Pre-SSE 4.1, we need to use runtime library calls for floating point rounding operations.
+set is_64bit
+set is_pic
+isa x86
+
+function %floor(f32) -> f32 {
+ebb0(v0: f32):
+    v1 = floor v0
+    return v1
+}
+; check: function %floor(f32 [%xmm0]) -> f32 [%xmm0] system_v {
+; check: sig0 = (f32) -> f32 system_v
+; check: fn0 = sig0 %FloorF32
+; check: v1 = call fn0(v0)