add FIPS mode from fork

This introduces this file: https://github.com/10gen/openssl/blob/master/fips.go
Which was pointed to from this issue: https://github.com/spacemonkeygo/openssl/issues/37

fips.go

@@ -0,0 +1,22 @@
+// +build cgo
+// +build -darwin
+
+package openssl
+
+/*
+#include <openssl/ssl.h>
+*/
+import "C"
+
+func FIPSModeSet(mode bool) error {
+	var r C.int
+	if mode {
+		r = C.FIPS_mode_set(1)
+	} else {
+		r = C.FIPS_mode_set(0)
+	}
+	if r != 1 {
+		return errorFromErrorQueue()
+	}
+	return nil
+}