* If the environment variable PHANTOMJS_DISABLE_CRASH_DUMPS
is set to any value, do not initialize Breakpad.
* On Mac and Linux, if the environment variable TMPDIR is set,
put the crash dumps there instead of in /tmp.
* On Windows, %TEMP% was already being honored, but streamline
the code for that.
* Move the code that initializes Breakpad, and the code to print
the crash messages, to their own module (src/crashdump.{h,cpp})
and RAII class (CrashHandler).
* Better wording of the crash message, particularly in the case where
Breakpad failed to write a minidump file; update URL of crash-reporting
guide.
* Generally less repetitive code. (Still way too many #ifdefs.)
Zack Weinberg