Improve performance of Kranc code generation

[ianhinder]

Kranc is now very slow to generate McLachlan. It is our impression that it used to be faster. This may be due to changes in Kranc, McLachlan or Mathematica. I have added some rudimentary profiling to Kranc; you can output a profile at the end of the Kranc run by calling Kranc with "kranc -p <script>". Functions defined using DefFn which take more than 1s to execute are listed, along with their inclusive execution time.