strace: Trivial improvements.

* Break in FlagsTypeHandler once we have cleared all flags.
 * Use sizeof(hex) instead of writing out the size again.
 * Place comment above variable name in patch_syscalls.

src/bin/debug/strace/TypeHandler.cpp

@@ -228,6 +228,8 @@ FlagsTypeHandler::RenderValue(Context &context, unsigned int value) const
 		string rendered;
 		FlagsList::const_reverse_iterator i = fList.rbegin();
 		for (; i != fList.rend(); i++) {
+			if (value == 0)
+				break;
 			if ((value & i->value) != i->value)
 				continue;
 
@@ -241,7 +243,7 @@ FlagsTypeHandler::RenderValue(Context &context, unsigned int value) const
 				rendered += " | ";
 
 			char hex[20];
-			snprintf(hex, 20, "%x", value);
+			snprintf(hex, sizeof(hex), "0x%x", value);
 			rendered += hex;
 		}
 		if (rendered.empty())

src/bin/debug/strace/strace.cpp

@@ -272,8 +272,9 @@ patch_syscalls()
 
 	for (size_t i = 0; i < sSyscallVector.size(); i++) {
 		Syscall *syscall = sSyscallVector[i];
-		const string returnTypeName = syscall->ReturnType()->TypeName();
+
 		// patch return type handlers
+		const string returnTypeName = syscall->ReturnType()->TypeName();
 		if (returnTypeName == "status_t" || returnTypeName == "ssize_t"
 				|| returnTypeName == "int") {
 			syscall->ReturnType()->SetHandler(create_status_t_type_handler());