Added a check to make sure variables in definitions are correct (i.e. they are disjoint from other roles).

Fixed a very subtle bug that sometimes occasionally caused multiple statements to be grouped into a single statement, resulting in nonsensical error messages despite having a well-formed theory.

Moved Amended-Needham Schroeder into done_examples (temporary measure until all of the example theories have been properly converted into the latest Maude-PSL version). Also removed Amended-NS which was just a differently named file of the same protocol as Amended-Needham-Schroeder, and therefore not necessary.

Initial commit to the public repository. Contains all the files needed to run Maude-PSL, as well as an examples directory, and a directory of the original npa-examples for use of comparisions with the Maude-PSL examples. Also contains a pdf file containing a description of the language.