Completely revised FreeType's make management.

. In all makefiles `/' is used as the path separator.  The
  conversion to the real path separators is done as late as
  possible using $(subst ...).

. $(HOSTSEP) no longer exists.  Now, $(SEP) gives the path separator
  for the operating system, and the new $(COMPILER_SEP) the path
  separator for the compiler tools.

. $(BUILD) has been renamed to $(BUILD_DIR).  In general, all
  directory variables end with `_DIR'.  The variants ending in `_'
  (like `BASE_' have been removed).

The following ChangeLog entries only describe changes which are
not related to the redesign.

* builds/beos/beos-def.mk (BUILD_DIR): Fix typo.
* builds/compiler/watcom.mk (LINK_LIBRARY): Fix linker call to avoid
overlong arguments as suggested by J. Ali Harlow
<ali@avrc.city.ac.uk>.
* builds/dos/dos-wat.mk: New file.
* builds/freetype.mk (FREETYPE_H): Include header files from the
`devel' subdirectory.

* builds/os2/os2-dev.mk, builds/unix/unixddef.mk,
builds/unix/unixddef.mk, builds/win32/w32-bccd.mk,
builds/win32/w32-dev.mk (BUILD_DIR): Fix path.

* builds/unix/configure.ac, builds/unic/configure: Updated.
* builds/unix/unix-def.in (DISTCLEAN): Add `freetype2.pc'.


* devel/ftoption.h: Updated.