help: add topic about evolution, based on text from evolve extension I've taken the text produced by `hg help evolution` when the evolve extension is enabled and made that available by the same command with just hg core. Changes I've made: * Added "(EXPERIMENTAL)" to the title. (That doesn't hide the topic from `hg help`, though.) * Replaced old-style `experimental.evolution=<names>` config by new-style `experimental.evolution.<name>=true`. * Replaces a "obsolete markers" by "obsolescence markers". * Removed most content from "Current feature status". When the evolve extension is enabled, its help text takes precedence. Differential Revision: https://phab.mercurial-scm.org/D10516

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