I worked well for almost 2 month and now .....
I can't compile any more!

I am using IDE 1.6.5 and V.M:1603.30.4.

Every time, with any possible  source code I got this error:
Arduino.h:In file included from
WString.h:from
Print.h:from
Stream.h:from
Wire.h:from
RTClib.cpp:from
HardwareSerial.h:72:37: error: expected class-name before '{' token
 class HardwareSerial*:public Stream {
HardwareSerial.h:103:15: error: 'Print' has not been declared
         using Print*:write; \\ pull in write(str) and write(buf, size) from Print
HardwareSerial.h:85:13: error: 'int HardwareSerial::available()' marked override, but does not override
:int available(void) override
HardwareSerial.h:86:13: error: 'int HardwareSerial::peek()' marked override, but does not override
:int peek(void) override
HardwareSerial.h:87:13: error: 'int HardwareSerial::read()' marked override, but does not override
:int read(void) override
HardwareSerial.h:89:14: error: 'void HardwareSerial::flush()' marked override, but does not override
:void flush(void) override
HardwareSerial.h:90:16: error: 'size_t HardwareSerial::write(uint8_t)' marked override, but does not override
:size_t write(uint8_t) override
Arduino.h:In file included from
WString.h:from
Print.h:from
Stream.h:from
Wire.h:from
RTClib.cpp:from
Esp.h:126:27: error: 'Stream' has not been declared
:bool updateSketch(Stream& in, uint32_t size, bool restartOnFail = false, bool restartOnSuccess = true)
Arduino.h:In file included from
WString.h:from
Print.h:from
Stream.h:from
Wire.h:from
RTClib.cpp:from
Updater.h:44:24: error: 'Stream' has not been declared
:size_t writeStream(Stream &data)
Updater.h:61:21: error: 'Stream' has not been declared
:void printError(Stream &out)
Using library SSIDPASSWORD version 0.0.0 in folder d:\users\pbecc\onedrive\Arduino\libraries\SSIDPASSWORD
Using library Wire version 1.0 in folder c2\libraries\Wire
Using previously compiled file: demcuv2\Wire\Wire.cpp.o
Error compiling libraries 

I may have done somethink wrong......
I was working so well and now ...  I can't go back!

Arduino IDE compile faultless .......!

Paolo

I have the impression that something went wrong in the core libraries(RTClib is part of core libraries...... it could have been my fault since I was struggling to resolve some porting error and i was navigating in all the way up to core libraries....some time you press a key and you may generate an error difficult to trace back!
On those library there should be a Read Only kind of protection!
In the mean time I have updated to last release:
Arduino IDE to 1.6.8
ESP8266 core libraries to the last release
Visual Micro to the last release 
and the problem desappear!
Thank you anyhow of your help!