swift234

Update the printf() implementation to match the May demo slides. Major
changes include: 

  - Each '%' in the format string is followed by some number of
    non-alpha characters (the "layout") and then an alpha character
    (the "kind"). The string and character are passed along to each
    FormattedPrintable's printFormatted() so they can do custom
    formatting
  - The Format struct is now used for the 'default' layout, which all
    of the standard libaries use
  - Added 'x' and 'o' custom formatting for formatting numbers in hex
    and octal, respectively. 'u' and 'l' can be used to print
    characters in uppercase or lowercase (String versions are yet to
    come).
  - The code for splitFormat()/printf() match what will be on the
    slides. They use the split operations to keep the whole thing
    linear, rather than performing inefficient slices.

There are some ugly hacks here due to <rdar://problem/11529601>.


Swift SVN r1980