Regenerate Makefile when Rules-* change, clean extracted cpp files.

po/Rules-data

@@ -1,5 +1,7 @@
 # Additional Makefile rule to extract object names from data files
 
+Makefile: Rules-data
+
 celestia.pot-update: ../data/data.cpp
 
 ../data/data.cpp: ../data/solarsys.ssc ../data/earth_locs.ssc ../data/world-capitals.ssc ../data/galaxies.dsc ../data/nearstars.stc
@@ -8,3 +10,8 @@ celestia.pot-update: ../data/data.cpp
 	grep \"Sol/Earth\" ../data/world-capitals.ssc | awk -F\" '{ print "_(\"" $$2 "\");" }' >> ../data/data.cpp
 	egrep '\"Milky Way\"|\"LMC\"|\"SMC\"' ../data/galaxies.dsc | awk -F\" '{ print "_(\"" $$2 "\");" }' >> ../data/data.cpp
 	egrep '\"Solar System Barycenter\"' ../data/nearstars.stc | awk -F\" '{ print "_(\"" $$2 "\");" }' >> ../data/data.cpp
+
+clean: clean-data
+
+clean-data:
+	rm -f ../data/data.cpp

po/Rules-kde

@@ -1,7 +1,14 @@
 # Additional Makefile rule to extract strings from KDE's rc and ui files.
 
+Makefile: Rules-kde
+
 celestia.pot-update: ../src/celestia/kde/rc.cpp
 
 ../src/celestia/kde/rc.cpp:
 	extractrc ../src/celestia/kde/*/*.rc > ../src/celestia/kde/rc.cpp
 	extractrc ../src/celestia/kde/*.ui >> ../src/celestia/kde/rc.cpp
+
+clean: clean-kde
+
+clean-kde:
+	rm -f ../src/celestia/kde/rc.cpp

po/Rules-win-resource

@@ -1,6 +1,13 @@
 # Additional Makefile rule to extract object names from windows resource files
 
-celestia.pot-update: ../src/celestia/res/resource_strings.cpp
+Makefile: Rules-win-resource
+
+celestia.pot-update: ../src/celestia/win32/res/resource_strings.cpp
 
 ../src/celestia/win32/res/resource_strings.cpp: ../src/celestia/win32/res/celestia.rc
 	./extract_resource_strings.pl < ../src/celestia/win32/res/celestia.rc > ../src/celestia/win32/res/resource_strings.cpp
+
+clean: clean-win-resource
+
+clean-win-resource:
+	rm -f ../src/celestia/res/resource_strings.cpp