Fixed header levels in markdown

Fixed header markup in README.md. Previously, header markup did not match levels in the content list.
Use FindCurses to find curses libraries

- Some systems have the FindCurses.cmake module to find
  the curses/ncurses libraries using find_package(). And
  in some CheckLibraries is not very reliable, so as
  fallback FindCurses is now used if no other option
  works.
Anchors and reorder in dependency lists of README.md

Dependency headers for OSes needed anchors to work with links from
content list. Reordered OSes in content list to match headers
(all Linuxes first, Mac OS X last)
Merge pull request #180 from pmandera/readme-links

Fixed headers and links to dependencies in README.md
Merge pull request #184 from equalsraf/tb-curses

Use FindCurses.cmake as fallback to find curses libraries
README: add note on RHEL/CentOS 6

Add note on autoconf >2.69 being required for compilation under
RHEL/CentOS.

Closes #178.
README.md: fix anchor tags for CentOS/RHEL section

MAke the use of anchor tags consistent for the change introduced in
5cd3cbe.
Import luajit 2.0.2 source tree

This will be used for testing and in the future for reimplementing vimscript as
a compile-to-lua language.