Lowered requirement of autoconf to 2.68

- 2.68 is the latest in Ubuntu 12.04, and it worked fine with it too.

- Also updated README.INSTALL to include information regarding
  NOCONFIGURE option of autogen.sh. Without it, one would call
  autogen.sh which will do the configuration, forcing the user to
  provide configuration options, rendering make menuconfig unnecessary.
  Otherwise, the user would see an error which would be fixed by
  make menuconfig, but it's not documented.

- Furthermore, m4/ltversion.m4 is automatically generated and is now
  removed.

- Autoconf detects my architecture as i686. For now, I put a symlink to
  i386, which should be fine.

Signed-off-by: Shahbaz Youssefi <ShabbyX@gmail.com>