Also escape other whitespace control characters

[czechboy0]

Currently we don't escape all characters in the 0x00 to 0x1F range, as the spec describes:

All Unicode characters may be placed within the
quotation marks except for the characters that must be escaped:
quotation mark, reverse solidus, and the control characters (U+0000
through U+001F).

We should escape them all, to properly conform.