[Gm2] gm2 compiler crash (ulm/std/TimeIO.mod) bugfix

[Gaius Mulley]

Hi,

I've just checked in some changes on the gcc-5.2.0 graft for gm2 which
allows the ulm/std/TimeIO.mod to build:


   * gm2/gm2-compiler/M2GenGCC.mod:  add location to
     BuildStartFunctionCode.  Add location to finishFunctionDecl.
     Add location to BuildEndFunctionCode.
   * gm2/gm2-gcc/m2decl.c:  add DECL_BY_REFERENCE
     to parameter which is passed by reference.
   * gm2/gm2-gcc/m2statement.c:  add location to
     BuildStartFunctionCode and BuildEndFunctionCode.
     Reset cfun and current_function_decl to NULL at
     the end of the BuildEndFunctionCode.
   * gm2/gm2-gcc/m2statement.def:  add location to
     BuildStartFunctionCode and BuildEndFunctionCode.
   * gm2/gm2-gcc/m2statement.h:  add location to
     BuildStartFunctionCode and BuildEndFunctionCode.
   * gm2/gm2-gcc/m2treelib.c:  m2treelib_get_set_field_des
     rewritten to obtain the address and then indirectly
     reference the value so that it can be placed on the lhs
     of an assignment.  (m2treelib_get_set_value) detect
     if lvalue is a POINTER_TYPE and if so then perform
     and indirection lookup before generation the component
     reference.
   * gm2/m2pp.c:  modified to include a bits boolean in
     the pretty state machine.  Which will be used to print
     useful TREE boolean flags.

regards,
Gaius