Fix and improve stdlib optimizations

docs/stdlib/string.md

@@ -54,7 +54,7 @@ It contains functions for handling strings in the screen encoding with the same
 
 ## pstring
 
-The `scrstring` module automatically imports the [`err` module](./other.md).
+The `pstring` module automatically imports the [`err` module](./other.md).
 
 It contains functions for handling length-prefixed strings in any 8-bit encoding.
 
@@ -62,6 +62,14 @@ It contains functions for handling length-prefixed strings in any 8-bit encoding
 #### `sbyte pstrcmp(pointer str1, pointer str2)`
 #### `void pstrcopy(pointer dest, pointer src)`
 #### `void pstrpaste(pointer dest, pointer src)`
-#### `word pstr2word(pointer str)`
 #### `void pstrappend(pointer buffer, pointer str)`
 #### `void pstrappendchar(pointer buffer, byte char)`
+#### `word pstr2word(pointer str)`
+
+Converts a length-prefixed string to a number. Uses the default encoding.
+Sets `errno`.
+
+#### `word pscrstr2word(pointer str)`
+
+Converts a length-prefixed string to a number. Uses the screen encoding.
+Sets `errno`.