Merge branch 'jc/mailmap-case-insensitivity'

The mailmap mechanism unnecessarily downcased the e-mail addresses
in the output, and also ignored the human name when it is a single
character name.

This now has become Eric Sunshine's series, even though it still is
under jc/ hierarchy.

* jc/mailmap-case-insensitivity:
  mailmap: style fixes
  mailmap: debug: avoid passing NULL to fprintf() '%s' conversion specification
  mailmap: debug: eliminate -Wformat field precision type warning
  mailmap: debug: fix malformed fprintf() format conversion specification
  mailmap: debug: fix out-of-order fprintf() arguments
  mailmap: do not downcase mailmap entries
  t4203: demonstrate loss of uppercase characters in canonical email
  mailmap: do not lose single-letter names
  t4203: demonstrate loss of single-character name in mailmap entry