make, scripts: Re-add files necessary for building ytools

Re-add everthing needed for building and packaging ytools. This is a
big commit, 2002 lines of code. It mostly consists of C/C++ machinery,
plus some documentation-related stuff.

Signed-off-by: Jan Lindemann <jan@janware.com>

make/depend.mk

@@ -0,0 +1,45 @@
+# variables
+DEPEND_CFLAGS               += -D__MAKEDEPEND__
+DEPEND_CXXFLAGS             += -D__MAKEDEPEND__
+DEPEND_MK                   += $(addprefix .,$(addsuffix .dep.mk, $(BUILD_OBJ)))
+
+ifeq ($(DEPEND_MK_INCLUDED),)
+
+all:
+clean: depclean
+
+# convenience targets
+dep: $(DEPEND_MK)
+depclean:
+	$(RM) -f .*.dep.mk
+
+$(DEPEND_MK): $(PREREQ_DONE)
+
+ifneq ($(DEPEND_MK),)
+  ifeq ($(MAKECMDGOALS),)
+  -include $(DEPEND_MK)
+  endif
+  ifneq ($(filter all,$(MAKECMDGOALS)),)
+  -include $(DEPEND_MK)
+  endif
+endif
+
+%.o: .%.o.dep.mk
+
+.%.o.dep.mk: %.cpp $(BUILD_HDR) $(SRC_H)
+	$(CC) -M $(FINAL_CXXFLAGS) $(FINAL_CPPFLAGS) $(DEPEND_CXXFLAGS) $< -o $@
+
+.%.o.dep.mk: %.cc $(BUILD_HDR) $(SRC_H)
+	$(CC) -M $(FINAL_CXXFLAGS) $(FINAL_CPPFLAGS) $(DEPEND_CXXFLAGS) $< -o $@
+
+.%.o.dep.mk: %.c $(BUILD_HDR) $(SRC_H)
+	$(CC) -M $(FINAL_CFLAGS) $(FINAL_CPPFLAGS) $(DEPEND_CXXFLAGS) $< -o $@
+
+show-vars: show-vars-depend-mk
+show-vars-depend-mk:
+	@echo DEPEND_MK = $(DEPEND_MK)
+	@echo BUILD_HDR = $(BUILD_HDR)
+	@echo SRC_H     = $(SRC_H)
+
+endif # DEPEND_MK_INCLUDED
+DEPEND_MK_INCLUDED          := true