systemtap prototype #3

- demonstrates partial parsing of hypothetical systemtap script
  language using hand-written simpe LL(1) recursive-descent parser
  and similar little lexer: parse.cxx, parse.h
- baby grammar examples under testsuite/parseok
- only "probe" top-level construct is parsed; "global" missing;
  no provider-oriented syntax provided yet
- use autotools-style configure; make; make check
- to see parse tree dump, use stdin: echo 'SCRIPT FRAGMENT' | ./stap