thumb program will abort if illegal memory access is detected
illegal accesses will always be logged even if the option is off
program will always abort on illegal PC fetch even if the option is off
fs package is an abstraction layer for those function in the standard os
package that are used by gopher2600. for non-wasm builds the functions
are fowarded straight to the os pacakge.
for wasm builds, the calls are swallowed.
the note about historical versions also being covered wasn't strictly
needed and was ugly. the LICENCE being in the root file from the very
first commit is sufficient.
the location of the configuration directory now depends on how the
binary is built. release versions of the binary will look for the
gopher2600 directory in the user's os configuration directory.
non-release versions will look for the .gopher2600 directory in the CWD.
paths.ResourcePath() will create the paths that don't exist
paths.ResourcePath() now clearly differentiates paths and files
added build target to the Makefile; disabled release target for now
