Userland: Add a 'test' utility

This adds an incomplete implementation of the test util, missing some
user/group checks, and `-l STRING`.
It also symlinks '[' to 'test'.

Base/usr/share/man/man1/test.md

@@ -0,0 +1,96 @@
+## Name
+
+test - checks files and compare values
+
+## Synopsis
+
+```**sh
+$ test expression
+$ test
+$ [ expression ]
+$ [ ]
+```
+
+## Description
+
+`test` takes a given expression and sets the exit code according to its truthiness, 0 if true, 1 if false.
+An omitted expression defaults to false, and an unexpected error causes an exit code of 126.
+
+If `test` is invoked as `[`, a trailing `]` is _required_ after the expression.
+
+## Expressions
+
+The expression can take any of the following forms:
+
+### Grouping
+
+* `( <expression> )` value of expression
+
+### Boolean operations
+
+* `! <expression>` negation of expression
+* `<expression> -a <expression>` boolean conjunction of the values
+* `<expression> -o <expression>` boolean disjunction of the values
+
+### String comparison
+
+* `<string>` whether the string is non-empty
+* `-n <string>` whether the string is non-empty
+* `-z <string>` whether the string is empty
+* `<string> = <string>` whether the two strings are equal
+* `<string> != <string>` whether the two strings not equal
+
+### Integer comparison
+
+* `<integer> -eq <integer>` whether the two integers are equal
+* `<integer> -ne <integer>` whether the two integers are not equal
+* `<integer> -lt <integer>` whether the integer on the left is less than the integer on the right
+* `<integer> -gt <integer>` whether the integer on the left is greater than the integer on the right
+* `<integer> -le <integer>` whether the integer on the left is less than or equal to the integer on the right
+* `<integer> -ge <integer>` whether the integer on the left is greater than or equal to the integer on the right
+
+### File comparison
+
+* `<file> -ef <file>` whether the two files are the same (have the same inode and device numbers)
+* `<file> -nt <file>` whether the file on the left is newer than the file on the right (modification date is used)
+* `<file> -ot <file>` whether the file on the left is older than the file on the right (modification date is used)
+
+### File type checks
+
+* `-b <file>` whether the file is a block device
+* `-c <file>` whether the file is a character device
+* `-f <file>` whether the file is a regular file
+* `-d <file>` whether the file is a directory
+* `-p <file>` whether the file is a pipe
+* `-S <file>` whether the file is a socket
+* `-h <file>`, `-L <file>` whether the file is a symbolic link
+
+### File permission checks
+
+* `-r <file>` whether the curent user has read access to the file
+* `-w <file>` whether the curent user has write access to the file
+* `-x <file>` whether the curent user has execute access to the file
+* `-e <file>` whether the file exists
+
+
+Except for `-h/-L`, all file checks dereference symbolic links.
+
+NOTE: Your shell might have a builtin named 'test' and/or '[', please refer to your shell's documentation for further details.
+
+
+## Options
+
+None.
+
+## Examples
+
+```sh
+# Conditionally do something based on the value of a variable
+$ /bin/test "$foo" = bar && echo foo is bar
+# Check some numbers
+$ /bin/test \( 10 -gt 20 \) -o \( ! 10 -ne 10 \) && echo "magic numbers!"
+```
+
+## See Also
+
+* [`find`(1)](find.md)