consider macro TORRENT_USE_IOSTREAM for sha1_hash iostream operators (#790)

include/libtorrent/sha1_hash.hpp

@@ -42,7 +42,9 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/assert.hpp"
 #include "libtorrent/aux_/byteswap.hpp"
 
+#if TORRENT_USE_IOSTREAM
 #include <iosfwd>
+#endif // TORRENT_USE_IOSTREAM
 
 #ifdef max
 #undef max
@@ -255,11 +257,15 @@ namespace libtorrent
 		return ret;
 	}
 
+#if TORRENT_USE_IOSTREAM
+
 	// print a sha1_hash object to an ostream as 40 hexadecimal digits
 	TORRENT_EXPORT std::ostream& operator<<(std::ostream& os, sha1_hash const& peer);
 
 	// read 40 hexadecimal digits from an istream into a sha1_hash
 	TORRENT_EXPORT std::istream& operator>>(std::istream& is, sha1_hash& peer);
+
+#endif // TORRENT_USE_IOSTREAM
 }
 
 namespace std {

src/sha1_hash.cpp

@@ -34,11 +34,15 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/aux_/cpuid.hpp"
 #include "libtorrent/hex.hpp" // to_hex, from_hex
 
+#if TORRENT_USE_IOSTREAM
 #include <iostream>
 #include <iomanip>
+#endif // TORRENT_USE_IOSTREAM
 
 namespace libtorrent
 {
+#if TORRENT_USE_IOSTREAM
+
 	// print a sha1_hash object to an ostream as 40 hexadecimal digits
 	std::ostream& operator<<(std::ostream& os, sha1_hash const& peer)
 	{
@@ -57,6 +61,8 @@ namespace libtorrent
 		return is;
 	}
 
+#endif // TORRENT_USE_IOSTREAM
+
 	int sha1_hash::count_leading_zeroes() const
 	{
 		int ret = 0;