[Gm2] shared library bug fix

[Gaius Mulley]

Hi,

I've finally tracked down a bug in shared library creation (-fPIC).
The bug would occur if you were to make an indirect procedure call in
a shared library (sigsegv).

  To this end the gm2/examples/gravity now works, the example builds a
shared library, Python loads the shared library and configures the
simulated environment and runs the tiny simulation.  This example uses
complex numbers, iso libraries, trig maths and appears to behave
correctly,

regards,
Gaius


   * gm2/examples/gravity/README:  New file.
   * These changes fix a critical shared library bug which was
   * exposed
     if an indirect procedure call was ever made.  It also
   * changes
     (fixes) the method whereby procedures are declared to gcc.
   * gm2/gm2/gccgm2.c:  function
   * gccgm2_BuildEndFunctionDeclaration
     has an additional parameter, ispublic.  Changes to
     gccgm2_BuildEndFunctionDeclaration to check consistency of
     the three boolean parameters.  New procedure
     (function_to_pointer_conversion)
   * gm2/gm2/gm2except.c:  changed to reflect new
     gccgm2_BuildEndFunctionDeclaration prototype.
   * gm2/gm2/m2.flex:  fixed bug found using valgrind
     (uninitialised field in structure).
   * gm2/m2pp.c:  m2pp_comment_header prints out the a header
     comment which contains the public, static, external tree
     booleans.
   * gm2/bnf/m2-3.bnf:  completed the Alignment ebnf changes.
   * gm2/bnf/m2-h.bnf:  completed the Alignment ebnf changes.
   * gm2/bnf/m2.bnf:  completed the Alignment ebnf changes.
   * gm2/el/g-mode.el:  close parenthesis detected.
   * gm2/examples/gravity/Makefile.in:  fixed rules and allow
     example to be built using post-install or pre-installed gm2.
   * gm2/examples/gravity/testsim.py:  fixed circle position.
   * gm2/examples/gravity/twoDsim.mod:  tidied up comments.
   * gm2/gm2-compiler/M2GCCDeclare.mod:  changes to reflect new
     gccgm2_BuildEndFunctionDeclaration prototype.  Also fixed a
     bug in IsEffectivelyImported which would attempt to declare
     a procedure if it were declared in another imported module.
   * gm2/gm2-compiler/SymbolTable.def:  tidied up declaration.
   * gm2/gm2-compiler/gccgm2.def:  new
   * BuildEndFunctionDeclaration
     declaration.