crash_reporter: Fix initial compile issues with Android toolchain

Fix some issues to get crash_reporter to compile on Android.

C++ source:
* bits/wordsize.h is used for __WORDSIZE, but is unavailable for most
  Android toolchain architectures.  It instead is available in sys/cdefs.h

Flex source:
* The Flex compiler toolchain doesn't link against the default fl library
  using -lfl.  Thus there is no yywrap() function defined.  Since the
  default fl library implementation just returns 1 (true), instead add a
  directive to disable yywrap.
* The index(..) function has been deprecated in favor of strchr(..)
* Add a directive to disable the "deprecated conversion from string constant
  to 'char*'" warning in the generated code.
* Remove warning suppression for the input() function which doesn't get
  generated with Flex v2.5.39 and the arguments passed in the build command.

Bug: 22874187
Change-Id: I6d7dcf5f801010aeae06db9f0628a6652ee269ee