made assert tied to the new TORRENT_DEBUG define. Fixed two include problems that surfaced as a result

include/libtorrent/assert.hpp

@@ -33,6 +33,11 @@ POSSIBILITY OF SUCH DAMAGE.
 #ifndef TORRENT_ASSERT
 
 #include "libtorrent/config.hpp"
+
+#if !defined TORRENT_DEBUG
+#define TORRENT_ASSERT(a) do {} while(false)
+#else
+
 #include <string>
 
 #ifdef __GNUC__
@@ -51,3 +56,5 @@ TORRENT_EXPORT void assert_fail(const char* expr, int line, char const* file, ch
 
 #endif
 
+#endif
+

include/libtorrent/lazy_entry.hpp

@@ -38,6 +38,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/assert.hpp"
 #include "libtorrent/size_type.hpp"
 #include <iosfwd>
+#include <string>
 
 namespace libtorrent
 {

src/gzip.cpp

@@ -35,6 +35,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "zlib.h"
 
 #include <vector>
+#include <string>
 
 namespace
 {