Convert remaining source files from ISO-8859-1 to UTF-8

Most were already converted.  Fixes error raised by FlawFinder in CI:
Error: encoding error in ./src/synaptics.c
'utf-8' codec can't decode byte 0xa9 in position 16: invalid start byte

Signed-off-by: Alan Coopersmith <>
6 jobs for CI in 2 minutes and 1 second (queued for 1 second)