If MSYS (with bash) is not installed on Windows then do the shell
variable substitution by ourselves. Otherwise just call bash to do the
job.

Currently the --config switch does not work because when loading
a new rebar config the global setting is ignored for all paths.
This patch provides a check when loading new rebar config to see
whether or not the current config path matches the `base_dir` set in
global conf, which produces the expected behaviour.

Added new property to `eunit_opts` option list:

  reset_after_eunit::boolean() - default = true.
      If true, try to "reset" VM state to approximate state prior to
      running the EUnit tests:
          * Stop net_kernel if it was started
          * Stop OTP applications not running before EUnit tests were run
          * Kill processes not running before EUnit tests were run
          * Reset OTP application environment variables

Previous patch erroneously assumed that cover:start() returned
{already_started,Pid} in the cases where cover was already started. We
now turn {error,{already_started,Pid}} into {ok, Pid} and return
{error, Reason} if we encounter an error we do not know about, this
will cause a nice and violent badmatch to stop everything.

Redirect cover module output to .eunit/cover.log

The cover module calls io:format and io:fwrite directly for several types of
informational messages and warnings.  When using meck to mock covered modules
these warnings are triggered and can cause severe polution of the test output.

We can avoid this by starting cover explicitly then setting the group_leader
of that process to a file handle.

Generate .hrl files into include from SNMP MIB files.
Change the order of so .mib files are built before .erl
This is necessary since .hrl files are generated from
the .mib files.
The generated .bin and .hrl files are deleted by clean.

This is a cleaned up version of a patch originally
sent to the rebar mailing list by David Nonnenmacher.

The ability to overload macros was added in Erlang R13B04.
The second form was not used anyway.

Skip appup generation for new app in release