Generated the mix.exs file through configure is not possible when using mix, as
it does not run configure after having downloaded the dependencies.
#621
to do so, we remove configure script from repository.
it must be generated with autotools.
for developpers not using autotools, we include the configure script in
release source tarball, which in generated with correct version string.
Use dynamic Rebar configuration
Make iconv dependency optional
Disable transient_supervisors compile option
Add hipe compilation support
Only compile ibrowse and lhttpc when needed
Make it possible to generate an OTP application release
Add --enable-debug compile option
Add --enable-all compiler option
Add --enable-tools configure option
Add --with-erlang configure option.
Add --enable-erlang-version-check configure option.
Add lager support
Improve the test suite