Add autoconf-based build infrastructure for tig

Add autoconf-based build infrastructure for tig

This is a first cut at building tig using autoconf. With this patch, tig
configures and builds on both Linux (FC4) and OS X.

Signed-off-by: Steven Grimm <koreth@midwinter.com>
Reworked to not use aclocal+automake and external scripts for
bootstrapping. Instead, run `make configure` to generate the configure
script. It will create a config.make file from config.make.in, which
contains variables set by the configure script. Update .gitignore to
list generated files.

Signed-off-by: Jonas Fonseca <fonseca@diku.dk>