add paramref for fast path for param access (e.g. $1, $(1))

still set "1" in Vars, for access like
 n := 1
 v := $($(n))

fix to set $0 to variable name in $(call )

after:
% ./run_integration_test.rb android
Running make for android... 5.62 secs
Running kati for android... 10.89 secs
android: OK

PASS!
4 files changed