pgmspace: zero out memory in strncpy_P (#2633)
pgmspace: zero out memory in strncpy_P (#2633)

strncpy should write 'size' characters, padding with zeroes if src is
shorter than 'size'.

Adam5Wu/Arduino,Adam5Wu/Arduino,Lan-Hekary/Arduino,wemos/Arduino,sticilface/Arduino,sticilface/Arduino,esp8266/Arduino,jes/Arduino,jes/Arduino,Lan-Hekary/Arduino,hallard/Arduino,me-no-dev/Arduino,hallard/Arduino,Juppit/Arduino,Adam5Wu/Arduino,esp8266/Arduino,sticilface/Arduino,sticilface/Arduino,Adam5Wu/Arduino,hallard/Arduino,me-no-dev/Arduino,Juppit/Arduino,me-no-dev/Arduino,lrmoreno007/Arduino,Adam5Wu/Arduino,Juppit/Arduino,Lan-Hekary/Arduino,Juppit/Arduino,hallard/Arduino,me-no-dev/Arduino,esp8266/Arduino,wemos/Arduino,hallard/Arduino,jes/Arduino,jes/Arduino,esp8266/Arduino,sticilface/Arduino,Lan-Hekary/Arduino,wemos/Arduino,lrmoreno007/Arduino,Juppit/Arduino,lrmoreno007/Arduino,esp8266/Arduino,jes/Arduino,wemos/Arduino,lrmoreno007/Arduino,me-no-dev/Arduino,wemos/Arduino,lrmoreno007/Arduino,Lan-Hekary/Arduino