Rewrite fileio functions to cater for a list of memory segments

[stefanrueger]

The fileio.c functions all have a granularity of the complete AVR memory, which matches what is needed in -U. In order to enable writing of memory intervals in the terminal this PR updates the I/O functions in fileio.c for later use.

Also fixes Issues #1390 and #1391.

[mcuee]

Tested to be good to fix Issue #1390 and #1391.

• Avrdude segfaults when writing ihex or srec files for some parts #1390 (comment)
• Avrdude creates srec files in an unnecessarily lax way #1391 (comment)

[mcuee]

Test using real programmer and not -c dryrun.

PS C:\work\avr\avrdude_test\avrdude_bin> .\avrdude_pr1392 -c urclock -p m328p -P COM35 -U .\hex\Blink.ino.standard.hex
avrdude_pr1392: AVR device initialized and ready to accept instructions
avrdude_pr1392: device signature = 0x1e950f (probably m328p)
avrdude_pr1392: Note: flash memory has been specified, an erase cycle will be performed.
                To disable this feature, specify the -D option.
avrdude_pr1392: erasing chip
                delaying chip erase until first -U upload to flash

avrdude_pr1392: processing -U flash:w:.\hex\Blink.ino.standard.hex:i
avrdude_pr1392: reading input file .\hex\Blink.ino.standard.hex for flash
                with 924 bytes in 1 section within [0, 0x39b]
                using 8 pages and 100 pad bytes
avrdude_pr1392: preparing flash input for device bootloader
avrdude_pr1392: writing 924 bytes flash ...
Writing | ################################################## | 100% 6.60 s
avrdude_pr1392: 924 bytes of flash written
avrdude_pr1392: verifying flash memory against .\hex\Blink.ino.standard.hex
Reading | ################################################## | 100% 5.25 s
avrdude_pr1392: 924 bytes of flash verified

avrdude_pr1392 done.  Thank you.

PS C:\work\avr\avrdude_test\avrdude_bin> .\avrdude_pr1392 -c urclock -p m328p -P COM35 -xshowall
avrdude_pr1392: AVR device initialized and ready to accept instructions
0 2022-06-10 21.21 Blink.ino.standard.hex 924 store 31298 meta 34 boot 512 o4.4 --s-h-r-- 
vector 0 (RESET) ATmega328P

PS C:\work\avr\avrdude_test\avrdude_bin> .\avrdude_pr1392 -c urclock -p m328p -P COM35 -U flash:r:read.srec:s
avrdude_pr1392: AVR device initialized and ready to accept instructions
avrdude_pr1392: device signature = 0x1e950f (probably m328p)

avrdude_pr1392: processing -U flash:r:read.srec:s
avrdude_pr1392: reading flash memory ...
Reading | ################################################## | 100% 5.31 s
avrdude_pr1392: writing output file read.srec

avrdude_pr1392 done.  Thank you.

PS C:\work\avr\avrdude_test\avrdude_bin> srec_cat .\read.srec -output read.bin -binary && echo OK
OK