oslib: make str* compat functions more uniform

oslib: make str* compat functions more uniform

- Ensure there are CONFIG_ guards in the headers and .c files because
  sometime utilities include oslib headers directly and reference oslib
  .c files in the Makefile
- Ensure all the oslib/str*.h files have redefinition guards
- Shuffle some #include lines from the .h files to the .c ones
- Ensure the <name>.c files have #include "<name>.h" in them so the
  compiler can check the declaration and definition match

Signed-off-by: Sitsofe Wheeler <sitsofe@yahoo.com>