Fix the permissions on many files marked executable

[maqifrnswa]

Many files (such as readme.txt, about.jpg, lots of C, header, and java files) were marked as executable (755). This pull sets them back to being non-executable (644).

[maqifrnswa]

In case you don't want to do a commit, the command to do the same thing is:
find . -type f -iname .jpg -or -iname *.java -or -iname *.pde -or -iname *.h -or -iname *.cpp -or -iname *.c -or -iname makefile -or -iname key.txt -or -iname pref_.txt -or -iname '_.txt' -print0 | xargs -0 chmod -x