Include cef_config.h from base/cef_build.h and fix detection of
args.gn changes so that defines are available everywhere by default.
Fix include configuration for chrome_elf_set and sandbox targets.
Set enable_alloy_bootstrap=false to build with Alloy bootstrap code
removed. Extension API is documented as deprecated in comments but
not compiled out with this arg.
Add the generated includes/ directory to CEF's "config" so that source files
included in patched Chromium targets (for example, blink_glue.cc) can find
cef_config.h which will be included via `include/internal/cef_types_linux.h`
on Linux.
- Crash reporting is enabled and configured using a "crash_reporter.cfg"
file. See comments in include/cef_crash_util.h and tools/crash_server.py
for usage.