Commit [35d338]ngspice partly reverted commit 423f9a9db to fix deletion

of source files if make was accidentally used in the source tree.
That caused the original bug to return.  Fix the problem by deleting
the generated source files by name (no such files exist in source.
Also make the generated files depend on cmpp, making 'make clean'
unnecessary after a chenge to cmpp.

src/xspice/icm/GNUmakefile.in

@@ -97,12 +97,12 @@ cm-descr := \
 
 # When recursively making clean, cm-objs and cm-gens do not contain
 # the files generated for individual code models, as cmpp has already gone
-# and modlist and udnlist are empty.  Those files are explicitly removed.
+# and modlist and udnlist are empty.  The files are explicitly removed.
 
 cm-clean :
 	-rm -f $(cm)/$(cm).cm
 	-rm -f $(cm-descr) $(cm-objs) $(cm-gens)
-	-rm -f $(cm)/*/*.o $(cm)/*/.deps/*
+	-rm -f $(cm)/*/ifspec.c $(cm)/*/cfunc.c $(cm)/*/*.o $(cm)/*/.deps/*
 	-rm -f $(cm-deps)
 
 cm-distclean :
@@ -135,10 +135,10 @@ $(cm-dirs) $(cm-dep-dirs) :
 %/cmextrn.h %/cminfo.h %/udnextrn.h %/udninfo.h %/objects.inc : $(srcdir)/%/modpath.lst $(srcdir)/%/udnpath.lst
 	CMPP_IDIR=$(srcdir)/$(@D) CMPP_ODIR=$(@D) $(CMPP) -lst
 
-%/ifspec.c : $(srcdir)/%/ifspec.ifs
+%/ifspec.c : $(srcdir)/%/ifspec.ifs $(cmpp)
 	CMPP_IDIR=$(srcdir)/$(@D) CMPP_ODIR=$(@D) $(CMPP) -ifs
 
-%/cfunc.c : $(srcdir)/%/cfunc.mod
+%/cfunc.c : $(srcdir)/%/cfunc.mod $(cmpp)
 	CMPP_IDIR=$(srcdir)/$(@D) CMPP_ODIR=$(@D) $(CMPP) -mod