Make quoteIfContainsWhite quote argument, so it can be safely passed to shell.

On Windows put it in double quotes and escape double quotes using backslash.
On Posix put it in single quotes and escape single quotes using '"'"'.

This commit changes what quoteIfContainsWhite does, but before that change it
was used incorrectly all over standard library, which caused security issues.
Merge pull request #702 from zielmicha/master

Make quoteIfContainsWhite quote argument, so it can be safely passed to shell.