Replace bleeding-edge libevent with libevhtp.

A libevhtp package exists for recent releases of Linux distros. An
exception for these will come in a future patch.

Change-Id: I15b96be469b91f19c06c326fc52b42027c097df9
Bug: 26850406
Bug: 24204638
Reviewed-on: https://weave-review.googlesource.com/2384
Reviewed-by: Vitaly Buka <vitalybuka@google.com>
diff --git a/Makefile b/Makefile
index de69f40..6fd30f5 100644
--- a/Makefile
+++ b/Makefile
@@ -88,7 +88,6 @@
 
 weave_obj_files := $(WEAVE_SRC_FILES:%.cc=out/$(BUILD_MODE)/%.o)
 
-# TODO(jacobmarble): There are too many gtest/gmock deps in non-test targets. Fix.
 $(weave_obj_files) : out/$(BUILD_MODE)/%.o : %.cc
 	mkdir -p $(dir $@)
 	$(CXX) $(DEFS_$(BUILD_MODE)) $(INCLUDES) $(CFLAGS) $(CFLAGS_$(BUILD_MODE)) $(CFLAGS_CC) -c -o $@ $<
@@ -102,7 +101,7 @@
 clean :
 	rm -rf out
 
-cleanall : clean clean-gtest clean-libevent
+cleanall : clean clean-gtest clean-libevhtp
 
 .PHONY : clean cleanall all