* re-compile rebar.erl instead of rebar_core to define VCS_INFO
* append "-dirty" if vcs indicates unclean repo status

1. manually insert directory entries to work around issues fixed in
   R15B02 erl_prim_loader
2. put the escript archive's beams in appname/appname/ebin

Tested with R13B03 and R15B01.

Use erl_prim_loader:read_file_info instead of filelib:is_file to make
sure paths inside the escript archive are handled properly.

When rebar ct executes with its default common test directory of "test",
it will generate a hardcoded "logs" directory in every application with
a test directory present, causing an overlap with eunit's test framework
so even test directories with only eunit tests will be processed by ct.

This allows the node to run in paths which include special characters,
for example 'C:\Program Files (x86)\Product Name'

We have to rename ?FAIL to ?ABORT once we require at least R13B04 for
building rebar. Macros with different arity were not supported by the
compiler before 13B04.