peekNextDigit() returns an int, so it can return -1 in addition to all
256 possible bytes. By putting the result in a signe char, all bytes
over 128 will be interpreted as "no bytes available". Furthermore, it
seems that on SAM "char" is unsigned by default, causing the
"if (c < 0)" line a bit further down to always be false.
Using an int is more appropriate.
A different fix for this issue was suggested in #1399. This fix helps
towards #1728.
Made some helper class for files filtering.
platforms.txt now contains only one platform at a time.
Some cleanup in Compiler and AvrDudeUploader classes.
Cristian Maglie
Matthijs Kooijman