de-lint code base: additional corrections of comparisons to $null

* place $null first within comparisons to avoid inadvertent array slicing
  - ref: PowerShell/PSScriptAnalyzer#200 @@ https://archive.is/Qxkc0 @@ https://webcitation.org/6du3Cd5TY

lib/core.ps1

@@ -444,7 +444,7 @@ function reset_aliases() {
 function CMD_SET_encode_arg {
     # CMD_SET_encode_arg( @ )
     # encode string(s) to equivalent CMD command line interpretable version(s) as arguments for SET
-    if ($args -ne $null) {
+    if ($null -ne $args) {
         $args | ForEach-Object {
             $val = $_
             $val = $($val -replace '\^','^^')

lib/install.ps1

@@ -283,7 +283,7 @@ function is_in_dir($dir, $check) {
 
 # hashes
 function hash_for_url($manifest, $url, $arch) {
-    $hashes = @(hash $manifest $arch) | where-object { $_ -ne $null };
+    $hashes = @(hash $manifest $arch) | where-object { $null -ne $_ };
 
     if($hashes.length -eq 0) { return $null }
 
@@ -509,7 +509,7 @@ function shim_def($item) {
 }
 
 function create_shims($manifest, $dir, $global) {
-    $manifest.bin | where-object { $_ -ne $null } | foreach-object {
+    $manifest.bin | where-object { $null -ne $_ } | foreach-object {
         $target, $name, $arg = shim_def $_
         write-output "creating shim for $name"
 
@@ -541,7 +541,7 @@ function rm_shim($name, $shimdir) {
 }
 
 function rm_shims($manifest, $global) {
-    $manifest.bin | where-object { $_ -ne $null } | foreach-object {
+    $manifest.bin | where-object { $null -ne $_ } | foreach-object {
         $target, $name, $null = shim_def $_
         $shimdir = shimdir $global