mk: rewrite the documentation handling.

This converts it to be very similar to crates.mk, with a single list of
the documentation items creating all the necessary bits and pieces.

Changes include:
- rustdoc is used to render HTML & test standalone docs
- documentation building now obeys NO_REBUILD=1
- testing standalone docs now obeys NO_REBUILD=1
- L10N is slightly less broken (in particular, it shares dependencies
  and code with the rest of the code)
- PDFs can be built for all documentation items, not just tutorial and
  manual
- removes the obsolete & unused extract-tests.py script
- adjust the CSS for standalone docs to use the rustdoc syntax
  highlighting

Author: huonw

mk/clean.mk

@@ -41,7 +41,6 @@ clean-misc:
 	@$(call E, cleaning)
 	$(Q)rm -f $(RUNTIME_OBJS) $(RUNTIME_DEF)
 	$(Q)rm -f $(RUSTLLVM_LIB_OBJS) $(RUSTLLVM_OBJS_OBJS) $(RUSTLLVM_DEF)
-	$(Q)rm -Rf $(DOCS)
 	$(Q)rm -Rf $(GENERATED)
 	$(Q)rm -Rf tmp/*
 	$(Q)rm -Rf rust-stage0-*.tar.bz2 $(PKG_NAME)-*.tar.gz $(PKG_NAME)-*.exe dist

mk/crates.mk

@@ -92,6 +92,7 @@ TOOL_SOURCE_rustc := $(S)src/driver/driver.rs
 ################################################################################
 
 DOC_CRATES := $(filter-out rustc, $(filter-out syntax, $(CRATES)))
+COMPILER_DOC_CRATES := rustc syntax
 
 # This macro creates some simple definitions for each crate being built, just
 # some munging of all of the parameters above.