text: Add text package with ascii, format, and utf modules.
io: Update in lieu of Volta changes.
conv: Add more conversions.
utf: Add an encode that takes a buffer as an argument.
text: Fix isHexDigit.
conv: Add base support to toInt.
conv: Add ConvException.
conv: First argument to toInt should be const(char)[].
text: Specify failure state in MalformedUTF8Exception.
text: Remove dead UTF import.