lib/Makefile.b32: updates

* Rename the object object directory from 'objs' to 'BCC_obj'. I feel
 it should be named properly. Ref. Makefile.Watcom where it's called
 'WC_Win32.obj'.

* Turn off these warnings to keep the build totally silent (with CBuilder-6
 that is).
  -w-inl    8026 Functions X are not expanded inline.
  -w-pia   8060 Possibly incorrect assignment
  -w-pin  8061 Initialization is only partially bracketed

I'm sure the warnings could be fixed the "proper" way or with some added
"#pragma" statements. But that just clutters the sources IMHO.

* $(MKDIR) and $(RMDIR) have been replaced with the shell-commands 'md'
 and 'rd'. When having MingW/Msys programs 'mkdir.exe' and 'rmdir.exe' in
$PATH, this confuses Borland's make and the result (the cleaning etc.) would
 not be as expected.

* Added a ".path.int = $(OBJDIR)" to tell make where the $(PREPROCESSED)
 files are. Why we need the preprocess step in the fist place is beyond me
(Yang?). But I'll leave that for now.