configure script also.
* builds/freetype.mk (INCLUDES): Add `OBJ_DIR'.
* builds/unix/detect.mk (have_mk): New variable to test for
external build.
(unix-def.mk): Defined according to value of `have_mk'.
* builds/unix/unix.mk (have_mk): New variable to test for
external build.
Select include paths for unix-def.mk and unix-cc.mk according
to value of `have_mk'.
* builds/unix/unix-def.in (OBJ_BUILD): New variable.
(DISTCLEAN): Use it.
* builds/unix/unix-cc.in (LIBTOOL): Define default value only
if not yet defined.
* builds/unix/install.mk (install): Use `OBJ_BUILD' for installing
freetype-config.
* configure: Don't depend on bash features.
(ft2_dir, abs_curr_dir, abs_ft2_dir): New variables (code
partially taken from Autoconf).
Build a dummy Makefile if not building in source tree.
* docs/INSTALL: Document it.
David Turner