Use the correct way to add more flags in implicit rule.
Use the correct way to add more flags in implicit rule in demo-program/Makefile.
Edit all Makefile to be able to build debug version.
Add dependency of object file(s) to depend on header file.
Edit Makefile to make target "release" (library only) the default target.
Opps! I don't need default in Makefile's .PHONY anymore.
Merge pull request #1 from peat-psuwit/Makefile_improvment

Makefile improvment

The Makefiles is now using correct way to add flags to cc/c++ and able to compile the debug build.