fix error handling in random.cpp and fix accidental openssl dependency

include/libtorrent/aux_/dev_random.hpp

@@ -62,7 +62,7 @@ namespace libtorrent { namespace aux {
 			if (ret != buffer.size())
 			{
 #ifndef BOOST_NO_EXCEPTIONS
-				throw system_error(error_code(EIO, system_category()));
+				throw system_error(errors::no_entropy);
 #else
 				std::terminate();
 #endif

include/libtorrent/error_code.hpp

@@ -433,6 +433,9 @@ namespace libtorrent
 			overflow,
 #endif
 
+			// random number generation failed
+			no_entropy = 200,
+
 			// the number of error codes
 			error_code_max
 		};

src/error_code.cpp

@@ -263,7 +263,11 @@ namespace libtorrent
 			"bencoded nesting depth exceeded",
 			"bencoded item count limit exceeded",
 			"integer overflow",
+			"",
+			"",
+			"",
 #endif
+			"random number generator failed",
 		};
 		if (ev < 0 || ev >= int(sizeof(msgs)/sizeof(msgs[0])))
 			return "Unknown error";

src/random.cpp

@@ -41,13 +41,12 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/aux_/win_crypto_provider.hpp"
 
 #elif defined TORRENT_USE_LIBCRYPTO
+
 extern "C" {
 #include <openssl/rand.h>
 #include <openssl/err.h>
 }
 
-#include <boost/asio/ssl/error.hpp>
-
 #endif
 
 #include "libtorrent/aux_/disable_warnings_pop.hpp"
@@ -98,8 +97,7 @@ namespace libtorrent
 			if (r != 1)
 			{
 #ifndef BOOST_NO_EXCEPTIONS
-				throw system_error(error_code(int(::ERR_get_error())
+				throw system_error(errors::no_entropy);
-					, boost::asio::error::get_ssl_category()));
 #else
 				std::terminate();
 #endif