move stdlib.sys to stdlib.shell

This is a clearer descriptor of this internal detail

Author: scivision

+stdlib/+sys/cpu_load.m +stdlib/+shell/cpu_load.m+stdlib/+sys/cpu_load.m renamed to +stdlib/+shell/cpu_load.m

@@ -1,4 +1,4 @@
-%% SYS.DEVICE get drive index
+%% shell.DEVICE get drive index
 %
 %%% Inputs
 % * p: path

+stdlib/+sys/create_symlink.m +stdlib/+shell/create_symlink.m+stdlib/+sys/create_symlink.m renamed to +stdlib/+shell/create_symlink.m

@@ -1,4 +1,4 @@
-%% SYS.FILE_CHECKSUM compute checksum of file
+%% shell.FILE_CHECKSUM compute checksum of file
 function [hash, cmd] = file_checksum(file, hash_method)
 
 switch lower(hash_method)

+stdlib/+sys/device.m +stdlib/+shell/device.m+stdlib/+sys/device.m renamed to +stdlib/+shell/device.m

@@ -1,12 +1,9 @@
-%% sys.get_max_open_files  Get process open-file soft limit via shell
+%% shell.get_max_open_files  Get process open-file soft limit via shell
 function omax = get_max_open_files()
 
 omax = [];
 
-if ispc()
-  omax = uint64(omax);
-  return
-end
+if ~ispc()
 
 [s, m] = system('ulimit -n');
 if s == 0
@@ -17,6 +14,8 @@
   end
 end
 
+end
+
 omax = uint64(omax);
 
 end