cmd/gc: suspend safemode during typecheck of inlined bodies.

Should be obviously correct.  Includes minimal test case.
A future CL should clear up the logic around typecheckok and importpkg != nil someday.

R=rsc, dsymonds, rsc
CC=golang-dev
https://golang.org/cl/5652057
diff --git a/test/safe/pkg.go b/test/safe/pkg.go
new file mode 100644
index 0000000..bebc43a
--- /dev/null
+++ b/test/safe/pkg.go
@@ -0,0 +1,16 @@
+// true
+
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// a package that uses unsafe on the inside but not in it's api
+
+package pkg
+
+import "unsafe"
+
+// this should be inlinable
+func Float32bits(f float32) uint32 {
+	return *(*uint32)(unsafe.Pointer(&f))
+}
\ No newline at end of file