Remove unwanted "garbage cleanup" logic in Makefiles.

GNUmakefile.in defined a macro "garbage" that seems to have been meant
as a suitable target for automatic "rm -rf" treatment, but it isn't
actually used anywhere (and indeed never was, AFAICT).

Moreover, we have concluded that the Makefiles shouldn't take it upon
themselves to remove files that aren't expected by-products of building,
so that doing anything like that would be against project policy anyway.
Hence, just remove the macro.

Grepping around finds another violation of that policy in ecpg/preproc,
so clean that up too.

Daniel Gustafsson (ecpg change by me)

Discussion: https://postgr.es/m/AFBEF63E-E19D-4EBB-9F08-4617CDC751ED@yesql.se

GNUmakefile.in

@@ -78,7 +78,6 @@ GNUmakefile: GNUmakefile.in $(top_builddir)/config.status
 
 distdir	= postgresql-$(VERSION)
 dummy	= =install=
-garbage = =*  "#"*  ."#"*  *~*  *.orig  *.rej  core  postgresql-*
 
 dist: $(distdir).tar.gz $(distdir).tar.bz2
 	rm -rf $(distdir)

src/interfaces/ecpg/preproc/Makefile

@@ -64,8 +64,6 @@ uninstall:
 
 clean distclean:
 	rm -f *.o ecpg$(X)
-# garbage from development
-	@rm -f core a.out
 
 # `make distclean' must not remove preproc.y, preproc.c, preproc.h, or pgc.c
 # since we want to ship those files in the distribution for people with