FindTheorems performance improvements (from Timothy Bourke)
* Prefilter the list of theorems based on the constants and
  free variables in Pattern search terms, before calling
  Pattern.matches_subterm.
* Apply filters successively rather than running each and
  then finding the intersection.
* Show the time taken to run a query.
## targets
default: Pure-System
images: 
test: Pure-System
all: images test
## global settings
SRC = $(ISABELLE_HOME)/src
OUT = $(ISABELLE_OUTPUT)
LOG = $(OUT)/log
USEDIR = $(ISABELLE_TOOL) usedir -v true -i false -d false -C false -D document
## IsarRef sessions
Pure-System: $(LOG)/Pure-System.gz
$(LOG)/Pure-System.gz: Thy/ROOT.ML ../antiquote_setup.ML		\
  Thy/Basics.thy Thy/Misc.thy Thy/Presentation.thy
	@$(USEDIR) -s System Pure Thy
## clean
clean:
	@rm -f $(LOG)/Pure-System.gz