Variables: implemented limits on number of variables in a scope, the length of variable names, size of variable values and the number of accesible match values.

Body: added test regarding empty bodies and fixed testsuite to flush the message context when the message is changed.

Body: fixed bug in the :raw transform, added much comment to the body extraction code and added a first simple test to the testsuite.

Include: symbol table for global variables now also includes locations for the first import/export of each known variable.

Testsuite: added RFC compliance tests for the variables extension and fixed use of wrong default comparator.

Fixed bug in the order of default argument processing. Variable strings were evaluated befor constant strings, which is wrong.