ngparse -- ngspice changes
==========================

ngparse replaces the slow part of ngspice's frontend (.lib/.inc extraction,
numparam substitution, .subckt expansion). It links in as a static library
(libngparse.a) driven by a thin glue layer; ngspice's own parser is untouched.
It is the default in an --enable-ngparse build; --no-ngparse falls back to the
old frontend for a run. Without --enable-ngparse the glue is a no-op.

All changes live on branch jfisher/ng_parse. Seven files -- 2 new, 5 modified.

NEW
  src/frontend/ngparse_glue.c
      The glue. Decides whether ngparse should handle a source, reads ngspice's
      ngbehavior (to pass PSpice mode through), calls the ngparse ABI, and
      writes the expanded deck to a temp netlist. A no-op without USE_NGPARSE.
  src/include/ngspice/ngparse_glue.h
      Glue interface.

MODIFIED
  src/frontend/inp.c
      The seam: in inp_spsource(), just before inp_readall(), divert it to read
      ngparse's expanded deck instead of the original file. Kept shallow so the
      rest of inp_readall (compat passes, numparam, renumbering) still runs.
  src/main.c
      Adds --no-ngparse (and a redundant --ngparse) plus the --help line.
  configure.ac
      Adds --enable-ngparse and --with-ngparse-dir; checks for libngparse.a and
      ngparse.h; defines USE_NGPARSE.
  src/frontend/Makefile.am
      Builds ngparse_glue.c; adds the ngparse include path.
  src/Makefile.am
      Links libngparse.a into ngspice and libngspice.

Enabling, PSpice mode, and measured results: see install.txt and comparison.txt.