There was a hack put into install-sh to call strip with the correct
options on Mac OS X. But that never worked, because configure
disabled stripping on that platform altogether. So remove that dead
code, and while we're at it, update install-sh to the latest upstream
source (from Automake).
Instead, set up the right strip options in programs.m4, so this now
actually works the way it was originally intended.
Update install-sh to that from Autoconf 2.63, plus our Darwin-specific
changes (which I simplified a bit). install-sh is now able to install
multiple files in one run, so we could simplify our makefiles sometime.
install-sh also now has a -d option to create directories, so we don't need
mkinstalldirs anymore.
Use AC_PROG_MKDIR_P in configure.in, so we can use mkdir -p when available
instead of install-sh -d. For consistency with the rest of the world,
the corresponding make variable has been renamed from $(mkinstalldirs) to
$(MKDIR_P).
