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

fix erlexec parameter

look for new and old versions in the target parent

default module appup instruction -> load_module

The target_dir config in reltool allows you to put your release in
a directory other than in ./NAME, so we should look in the parent
directory of that to find the new and old versions instead of
simply looking in ./

Move untaring and retaring into a temporary path instead of in ./
to prevent name collisions with "releases" and "lib" that might
exist already. Having a subdirectory rel/releases/ can be useful.

Allows customizing the arguments handed over to the Erlang VM, e.g. to
set a name or a cookie, e.g. by setting escript_emu_args to:

%%! -name rebar -setcookie rebar

Use "%~f0" to get the full path of rebat.bat to correctly locate the
rebar script. Also put the script name in quotes when passing it to
escript.exe to correctly handle paths with spaces.