Code sync and fixed compile error for Mbed OS5

Dependencies:   DHT

Changes

RevisionDateWhoCommit message
3:264755aa4608 2019-11-08 Daniel_Lee Update; default tip
2:81340dde3444 2019-11-08 Daniel_Lee Fork and code sync with Mbed OS5;
1:6bcb143683f3 2015-03-10 sam_grove Update URL of DHT library
0:c12c28a0f9e7 2014-08-15 sam_grove Initial commit