stringutil: refactor core of pprint so it emits chunks This commit splits the core of pprint() to a new function that is a generator of chunks instead of a function returning a single value. This will make it possible to stream output without waiting for all data to be formatted first. And it will make it easier to implement support for indenting. Differential Revision: https://phab.mercurial-scm.org/D4397

BasedOnStyle: LLVM
IndentWidth: 8
UseTab: ForIndentation
BreakBeforeBraces: Linux
AllowShortIfStatementsOnASingleLine: false
IndentCaseLabels: false
AllowShortBlocksOnASingleLine: false
AllowShortFunctionsOnASingleLine: false
IncludeCategories:
  - Regex:           '^<'
    Priority:        1
  - Regex:           '^"'
    Priority:        2