clean up documentation and provide "doc" as alternative target for "docs"

* Makefile: make documentation follow the implementation.

* targets.mk: add "doc" as alternative target for "docs" to adhere
  more closely to standards
some fixes

Makefile

@@ -9,8 +9,8 @@ all::
 .PHONY:	targets help
 targets help:
 	$(info )
-	$(info make               - show this help)
-	$(info make all           - cleanly compile Org ELisp files and documentation)
+	$(info make help          - show this help)
+	$(info make               - cleanly compile Org ELisp files and documentation)
 	$(info )
 	$(info Installation)
 	$(info ============)
@@ -20,7 +20,7 @@ targets help:
 	$(info )
 	$(info Maintenance)
 	$(info ===========)
-	$(info make docs          - make all documentation)
+	$(info make doc           - make all documentation)
 	$(info make info          - make Info documentation)
 	$(info make html          - make HTML documentation)
 	$(info make pdf           - make pdf documentation)

targets.mk

@@ -59,7 +59,7 @@ install:	$(INSTSUB)
 
 install-info:	install-doc
 
-docs:	info html pdf card
+doc docs:	info html pdf card
 
 info html pdf card:
 	$(MAKE) -C doc $@