Root Makefile enhancements

This commit contains the following fixes and enhancements to the
root Makefile:

 * coreall: add dependency on runtime
 * all: before this commit, this target was depending on runtime and started
   by making coreall. This commit simplifies this and just makes this target
   depend on coreall, which is both simpler and semantically more accurate.
 * compare: let this target exit if the comparison fails
 * bootstrap: this commit removes the final invocation to make compare.
   The comparison was actually done twice, (1) as the final step of coreboot
   and (2) as the final step of bootstrap. The motivation for that was to
   ensure that the comparison messages were not lost and did appear last.
   Actually, it turns out that if the comparison fails, it makes no
   sense to continue the bootstrap process. That's why compare now exits
   immediately when it fails and there is thus no need to perform it twice.
 * Get rid of backup and restore targets which have become obsolete
   with the use of a revision control system

Makefile

@@ -398,7 +398,7 @@ coldstart:
 
 # Recompile the core system using the bootstrap compiler
 .PHONY: coreall
-coreall:
+coreall: runtime
 	$(MAKE) ocamlc
 	$(MAKE) ocamllex ocamlyacc ocamltools library
 
@@ -408,30 +408,15 @@ core:
 	$(MAKE) coldstart
 	$(MAKE) coreall
 
-# Save the current bootstrap compiler
-.PHONY: backup
-backup:
-	$(MKDIR) boot/Saved
-	if test -d $(MAXSAVED); then rm -r $(MAXSAVED); fi
-	mv boot/Saved boot/Saved.prev
-	mkdir boot/Saved
-	mv boot/Saved.prev boot/Saved/Saved.prev
-	cp boot/ocamlrun$(EXE) boot/Saved
-	cd boot; mv ocamlc ocamllex ocamlyacc$(EXE) Saved
-	cd boot; cp $(LIBFILES) Saved
-
-# Restore the saved bootstrap compiler if a problem arises
-.PHONY: restore
-restore:
-	cd boot; mv Saved/* .; rmdir Saved; mv Saved.prev Saved
-
 # Check if fixpoint reached
 .PHONY: compare
 compare:
 	@if $(CAMLRUN) tools/cmpbyt boot/ocamlc ocamlc \
          && $(CAMLRUN) tools/cmpbyt boot/ocamllex lex/ocamllex; \
 	then echo "Fixpoint reached, bootstrap succeeded."; \
-	else echo "Fixpoint not reached, try one more bootstrapping cycle."; \
+	else \
+	  echo "Fixpoint not reached, try one more bootstrapping cycle."; \
+	  exit 1; \
 	fi
 
 # Promote a compiler
@@ -493,8 +478,6 @@ opt.opt:
 # Core bootstrapping cycle
 .PHONY: coreboot
 coreboot:
-# Save the original bootstrap compiler
-	$(MAKE) backup
 # Promote the new compiler but keep the old runtime
 # This compiler runs on boot/ocamlrun and produces bytecode for
 # byterun/ocamlrun
@@ -515,8 +498,7 @@ coreboot:
 # Recompile the system using the bootstrap compiler
 
 .PHONY: all
-all: runtime
-	$(MAKE) coreall
+all: coreall
 	$(MAKE) ocaml
 	$(MAKE) otherlibraries $(WITH_DEBUGGER) $(WITH_OCAMLDOC) ocamltest
 
@@ -526,7 +508,6 @@ all: runtime
 .PHONY: bootstrap
 bootstrap: coreboot
 	$(MAKE) all
-	$(MAKE) compare
 
 # Compile everything the first time