Alloc CONFIG_FS_READABLE/WRITABLE to be defined in Kconfig files while preserving backward compatibility with legacy configurations (for the time being)

LPC31: Configuration and build support for a forthcoming USB host driver; configs/ea3131/nsh converted to use kconfig-frontend tools

Various fixes from initial attempts to integrate the SAMA5 SSC/I2C driver with the I2C character driver loopback test