add a changelog for Benjamin Reed's git patch (OS X build fixes)

add a changelog for Benjamin Reed's git patch (OS X build fixes)

* configure.in: Platform build fixes for Mac OS X
  the Darwin linker does not understand the -z option; wrap it in
  a check for $with_gnu_ld.
  environ is only available at runtime, so you need to make a
  reference to _NSGetEnviron instead for symbols to resolve properly.