Bump version number in preparation for a release

Rules.mak

@@ -54,7 +54,7 @@ HOSTCFLAGS=-O2 -Wall
 # this stuff alone.
 MAJOR_VERSION:=0
 MINOR_VERSION:=9
-SUBLEVEL:=20
+SUBLEVEL:=21
 VERSION:=$(MAJOR_VERSION).$(MINOR_VERSION).$(SUBLEVEL)
 # Ensure consistent sort order, 'gcc -print-search-dirs' behavior, etc. 
 LC_ALL:= C