Correct warning

Author: sandeepmistry

src/Modem.cpp

@@ -106,7 +106,7 @@ void ModemClass::noDebug()
   _debug = false;
 }
 
-int ModemClass::autosense(int timeout)
+int ModemClass::autosense(unsigned int timeout)
 {
   for (unsigned long start = millis(); (millis() - start) < timeout;) {
     if (noop() == 1) {

src/Modem.h

@@ -40,7 +40,7 @@ class ModemClass {
   void debug();
   void noDebug();
 
-  int autosense(int timeout = 10000);
+  int autosense(unsigned int timeout = 10000);
 
   int noop();
   int reset();