Add utilities for processing Linux core dump files.

This patch is part of a bigger patch that helps merging the breakpad code
with the modified version in Chromium OS.

Specifically, this patch makes the following changes:
1. Add an ElfCoreDump class for processing Linux core dump files, which will
   later be used to implement the core dump to minidump conversion.
2. Add a CrashGenerator class for generating a crash with a core dump file
   for testing the functionalities of ElfCoreDump.
3. Move some utility functions for reading/writing files to file_utils.h.

BUG=455
TEST=Tested the following:
1. Build on 32-bit and 64-bit Linux with gcc 4.4.3 and gcc 4.6.
2. Build on Mac OS X 10.6.8 with gcc 4.2 and clang 3.0 (with latest gmock).
3. All unit tests pass.
Review URL: http://breakpad.appspot.com/337001

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@900 4c0a9323-5329-0410-9bdc-e9ce6186880e
11 files changed