gperf dependency not documented

[Gavin Smith]

The DEPENDENCIES file in gnulib states a module that depends on the gperf
program:

* GNU gperf 3.0.1 or newer.
  + 3.0.1 or newer is mandatory, but 3.1 or newer is recommended.
    Needed if you use the 'iconv_open' module.

However, it is not the only module that uses this program.  gperf is
also listed as a dependency of the following modules:

unicase/locale-language
unicase/special-casing
uninorm/composition
unictype/joiningtype-byname
unictype/category-byname
unictype/combining-class-byname
unictype/property-byname
unictype/joininggroup-byname
unictype/incb-byname
unictype/bidiclass-byname
unictype/scripts

Should these be added to DEPENDENCIES?