Use PRUnichar for Gecko < 29, char16_t otherwise.

See https://bugzilla.mozilla.org/show_bug.cgi?id=927728
updating firefox prebuilts, thanks jleyba for fixing the build!
Bumping python version number
Bumping Version numbers to 2.42
typo
Merge branch 'master' of https://github.com/SeleniumHQ/selenium

# By AutomatedTester (2) and others
# Via AutomatedTester
* 'master' of https://github.com/SeleniumHQ/selenium:
  Bumping Version numbers to 2.42
  Bumping python version number
  updating firefox prebuilts, thanks jleyba for fixing the build!
  Use PRUnichar for Gecko < 29, char16_t otherwise.