Fixes the remaining test in test/db/cmd/cmd_c on big endian hosts,
tested on OpenBSD/sparc64.
The mask calculation was removed because it was unnecessary (only
comparing selected bytes anyway) and wrong by a factor of 8 (bits vs.
bytes confusion).
* Create new category for shell commands in new shell
* Port `env` and `exit`
* Port `ls`, `rm`, `sleep`, `uniq`, `uname` to new shell
* Rename `cname`s for shell commands
* Port `cp`, `cp.` and `echo`
* Port `cd` to newshell
* Add `~` (paths relative to home) handling in `rz_sys_chdir`
* Add `RZ_NONNULL` for `rz_sys_chdir`
* Port `cat`
* Port `mv` and `mkdir` to new shell; Remove old handlers
* Port `pwd`
* Port `sort`
* Remove `cp.` command
* Add `RZ_NONNULL` for arguments of `rz_syscmd_*` functions
* Port `cls` and `clear`
* cd to home when no argument provided
* Fix `mkdir`
* Add alias handling for `cat`
* Fix `mv` command