install: shell parameter expansions can be used in directory names

install: shell parameter expansions can be used in directory names

Fixes automake bug#11232.

GNU automake used to support shell parameter expansion and command
substitutions in installation directories, but that was inadvertently
broken by commit v1.11-759-g368f1c4 "install: don't create empty dirs
when an empty 'foo_PRIMARY' is used" of 18-03-2012, where shell quoting
of generated MKDIR_P command was changed from double to single quotes
in 3 places, while some 21 other places still use double quotes for
generated MKDIR_P commands.

* lib/am/data.am: Use double quotes for generated "mkdir -p" commands.
* lib/am/libs.am: Likewise.
* lib/am/ltlib.am: Likewise.

Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>