Changeset 6c77bba in rtems for aclocal/mkdir.m4

New autoconf feature from Ralf Corsepius:

It adds make rules for reconfiguring build-trees ("make Makefile") and
adds dependency rules for configure and friends (i.e. calls autoconf).
Most of this code has been "borrowed" from automake and was adapted to
rtems.

Addionally, I added automatic generation of the "aclocal.m4"-file by
"aclocal" (from the automake package). Therefore I splitted aclocal.m4
into several separate files (attached to this mail), each containing one
of rtems customized autoconf/m4-macros and have put them into a new
subdirectory "aclocal". Normal users won't be influenced and won't even
need this, unless they try to modify configure.in.

The main advantage of this is: these aclocal/m4-macros become reusable
and easier to administer. As a disadvantage, rtems becomes dependent of
having aclocal/automake installed. To keep building rtems functional if
autoconf or aclocal isn't installed, the related Makefile commands are
prefixed by "-" -- only an error message should be issued by "make".