This aligns the autotools build with the cmake build, which doesn't have
a config.h file. It also removes the ambiguity of config.h and
other/bootstrap_daemon/src/config.h.
- CFLAG gnu99 was changed to c99.
- CXXFLAG c++98 was changed to c++11.
- CFLAG -pedantic-errors was added so that non-ISO C now throws errors.
- _XOPEN_SOURCE feature test macro added and set to 600 to expose SUSv3
and c99 definitions in modules that required them.
- Fixed tests (and bootstrap daemon logging) that were failing due to
the altered build flags.
- Avoid string suffix misinterpretation; explicit narrowing conversion.
- Misc. additions to .gitignore to make sure build artifacts don't wind
up in version control.
Also added a `tox_options_copy` function for cloning an options object.
This can be useful when creating several Tox instances with slightly
varying options.
