add interactive serial communication code (from wikibooks.org)
modified:   Makefile: add compilation of interactive_serial.c .
new file:   interactive_serial.c: interactive serial communication code (from wikibooks.org) with 8n1 setup: data bit: 8, parity: none, stop bit: 1, baud rate: 115200 .
modified:   serialCOM.h: add debug messages for CR+LF .
modified:   serial_get.help.output: auto-updated.
modified:   serial_put.help.output: auto-updated.
add interactive example.
modified:   _info.txt: add a communication sequence with a light power meter using interactive program.