Quotes a string so that the shell (/bin/sh) will interpret the
quoted string to mean
If you pass a filename to the shell, for example, you should first quote it with this function.
The return value must be freed with g_free().
The quoting style used is undefined (single or double quotes may be used).
A literal string.
|The data is owned by the caller of the function.|
|The value is a file system path, using the OS encoding.|