Handle special characters in Shlex better

[ascopes]

I want to change how shell quoting is handled in src/main/**/platform/Shlex.java so that it can cope with parameters that have characters like \r and \n in them on the off-chance the user has some kind of really obscure path requirements somewhere.

If this happens, the argument needs to be changed to the format $'\\r' around those characters to ensure they are escaped properly.

For example

Given	Expect
\r	''$'\\r'''
hello\nworld	'hello'$'\\n''world'

Note that \\r is a Java-escaped string, which would print literally as \r, whereas \r itself implies a carriage return character literal.

We also need to handle binary sequences I guess.