I2C bus reset with info to user

I2C slave might stil have something to send when ESP826 starts I2C, thus
keeping the bus stuck.
Happens e.g. when power failure/reset during transmission.
Thanks to work of drmpf there is a solution.
Implemented as separate method so as not to interfere with existing.
Usage:

Wire.begin();
if (Wire.status() != I2C_OK) Serial.writeln("Something wrong with I2C
bus that cannot be recovered. Perform power cycle or search for other
masters on bus.";

libraries/Wire/Wire.h

@@ -62,6 +62,7 @@ class TwoWire : public Stream
     uint8_t endTransmission(void);
     uint8_t endTransmission(uint8_t);
     size_t requestFrom(uint8_t address, size_t size, bool sendStop);
+	uint8_t status();
 
     uint8_t requestFrom(uint8_t, uint8_t);
     uint8_t requestFrom(uint8_t, uint8_t, uint8_t);