Merge branch 'jk/banned-function'

It is too easy to misuse system API functions such as strcat();
these selected functions are now forbidden in this codebase and
will cause a compilation failure.

* jk/banned-function:
  banned.h: mark strncpy() as banned
  banned.h: mark sprintf() as banned
  banned.h: mark strcat() as banned
  automatically ban strcpy()