Adopt libxutils to add various built-ins, especially cross-platform filesystem operations

[jaromil]

Very nice to have a good number of utility functions from https://github.com/kala13x/libxutils

It is also configurable by modules:

USE_ARRAY=y
USE_CRYPT=y
USE_XTIME=y
USE_EVENT=y
USE_LIST=y
USE_XBUF=y
USE_HASH=y
USE_SOCK=y
USE_XLOG=y
USE_XSTR=y

[jaromil]

Added XArray succesfully now using only a few functions, makes sense to wrap it into cjit_ namespace in the close future and expose it to compiled programs as a handy extension. It should be an opinionated exposure of functions following best-practices in C secure coding (XArray allows a lot of flexibility on how memory is allocated...)