Slight change to the semantics so that global vars can be modified
from within a macro.

- Replace the parser with a happy one
- simplify the grammar in a couple of places
- don't automatically print out the argument to 'run'.

- Fix a bug in the 'defined' operator
- Print fewer newlines

Random hackage, including:

 - use the GetOpt library rather than hand-coded option parsing
 - change the binding syntax from --$var=value to just var=value.
 - be more informative in a couple of error messages

Changes to support comparing against summaries of previous runs:
  --save-summary=<file>      saves a summary of this run <file>
  --compare-summary=<file>   compares this run against summary from <file>

Implement a missing case in doStmt.

Print the outcome for each test as soon as it is known.  Makes
debugging the testsuite a lot easier.

Add support for piping arbitrary strings through arbitrary programs.

Command-line enhancements:
* Restrict the run to specific test(s).
* Allow variables to be set at the command line.

More minor tweaks.

Many improvements and debuggings.  The test driver now works as
desired, with multiple tests described in each .T file, and with the
test driver having a minimum of hardwired logic.

Onwards and upwards (allegedly).

Yet another major rewrite of the test driver.

Save today's work in a safe of placety, in view of the catastrophically
bad current state of our main NFS server.

Changes to support running "vanilla" tests -- those with a single source
file, reference .stdin, .stdout and maybe .stderr files.  These constitute
the vast majority of GHC tests.

#ifdef the import location for `trace' depending on build compiler.

Driver and infrastructure files (.T's) for the new test framework.