Add prologue-epilogue test that exercises new instructions and binary emission.

cranelift/filetests/isa/intel/prologue-epilogue.cton

@@ -0,0 +1,25 @@
+test legalizer
+test binemit
+set is_64bit=1
+isa intel haswell
+
+function %foo(f64 [%xmm0], i64 fp [%rbp], i64 csr [%rbx], i64 csr [%r12]) -> i64 csr [%r12] {
+    ss0 = local 168, offset 0
+    ss1 = incoming_arg 32, offset -32
+    
+ebb0(v0: f64 [%xmm0], v1: i64 [%rbp], v2: i64 [%rbx], v3: i64 [%r12]):
+    x86_push v1 ; bin: 40 55
+    copy_special %rsp -> %rbp ; bin: 48 89 e5
+    x86_push v2 ; bin: 40 53
+    x86_push v3 ; bin: 41 54
+    adjust_sp_imm -168 ; bin: 48 81 c4 ffffff58
+
+    ; ... function body ...
+
+
+    adjust_sp_imm +168 ; bin: 48 81 c4 000000a8
+    [-,%r12] v100 = x86_pop.i64 ; bin: 41 5c
+    [-,%rbx] v101 = x86_pop.i64 ; bin: 40 5b
+    [-,%rbp] v102 = x86_pop.i64 ; bin: 40 5d
+    return v102
+}