Some docs issues

I'm going through all signatures for the argument parser. I found some issues in the docs:

• join should be join [OPTION]... FILE1 FILE2
• cut should be cut OPTION... [FILE]...
• mkdir should be mkdir [OPTION]... DIRECTORY... (for some reason it says [USER] now 😄 )
• The usage string for everything based on hashsum are missing.
• more now says more [OPTIONS] <FILE>... which matches util-linux but uses a different syntax than GNU, which would be more [OPTIONS]... FILE...
• nohup FLAG should be nohup OPTION
• pr should be pr [OPTION]... [FILE]...
• printenv should be printenv [OPTION]... [VARIABLE]...
• printf should have the strings printf FORMAT [ARGUMENT]... and printf OPTION
• basenc has a " at the end of the usage string that shouldn't be there.
• runcon has "; at the end of the usage string that shouldn't be there.
• shuf has ; at the end of the usage string that shouldn't be there.
• sum has " at the end of the usage string that shouldn't be there.
• The last three lines of test's usage string should be written with [ instead of test.
• uniq should be uniq [OPTION]... [INPUT [OUTPUT]]
• unlink should be unlink FILE and unlink OPTION
• vdir is missing documentation

Use the issue checklist to identify the remaining work: usage strings for utilities based on hashsum, the final lines of test's usage string, and missing vdir documentation. Locate the argument-parser documentation or command definitions, verify the existing completed entries for consistency, and consider the work done when the unchecked items match the requested signatures and documentation style.