libcore_to_document and junit_to_document are no longer functions.

They are evaluated only once in the corresponding export .mk file.
This fixes build log spam reported in:
https://code.google.com/p/android/issues/detail?id=63184

Change-Id: I549eb052272bbdebef8fca697822f5eaa0fe5764
diff --git a/Android.mk b/Android.mk
index 166db4ee..1802239 100644
--- a/Android.mk
+++ b/Android.mk
@@ -457,8 +457,8 @@
 # Common sources for doc check and api check
 common_src_files := \
 	$(call find-other-html-files, $(html_dirs)) \
-	$(addprefix ../../libcore/, $(call libcore_to_document, $(LOCAL_PATH)/../../libcore)) \
-	$(addprefix ../../external/junit/, $(call junit_to_document, $(LOCAL_PATH)/../../external/junit))
+	$(addprefix ../../libcore/, $(libcore_to_document)) \
+	$(addprefix ../../external/junit/, $(junit_to_document))
 
 # These are relative to frameworks/base
 framework_docs_LOCAL_SRC_FILES := \