simplified to "2*a.i*a.i".
* Added canonicalize_clifford() function that can be helpful when comparing
expressions containing Dirac matrices.
+* Added a new function match() for performing pattern matching. subs() and
+ has() also accept patterns as arguments. A pattern can be any expression,
+ optionally containing wildcard objects. These are constructed with the
+ call "wild(<unsigned>)" and are denoted as "$0", "$1" etc. in the output
+ and in ginsh.
* Fixed possible crash when calling subs() on expressions with non-commutative
products.