add descripition fo "hoogle" use flag about gentoo-haskell HOT 2 CLOSED

$ euse -i -g hoogle
global use flags (searching: hoogle)
************************************************************
[-      ] hoogle - generate hoogle database for dev-haskell/hoogle

$ equery u texmath
[ Legend : U - final flag setting for installation]
[        : I - package is installed with flag     ]
[ Colors : set, unset                             ]
 * Found these USE flags for dev-haskell/texmath-0.8.4.2:
 U I
 + + doc         : Add extra documentation (API, Javadoc, etc). It is recommended to enable per package instead of globally
 - - executable  : Compile test executable.
 - - hoogle      : <unknown>
 + + hscolour    : Include coloured haskell sources to generated documentation (dev-haskell/hscolour)
 + + network-uri : Get Network.URI from the network-uri package.
 + + profile     : Add support for software performance analysis (will likely vary from ebuild to ebuild)
 + + test        : Workaround to pull in packages needed to run with FEATURES=test. Portage-2.1.2 handles this internally, so
                   don't set it in make.conf/package.use anymore

fquery u arithmoi
USE flags for dev-haskell/arithmoi-0.4.1.3
 + doc      : Add extra documentation (API, Javadoc, etc). It is recommended to enable per package instead of globally
   hoogle   : << no description >>
 + hscolour : Include coloured haskell sources to generated documentation (dev-haskell/hscolour)
 + profile  : Add support for software performance analysis (will likely vary from ebuild to ebuild)
 + test     : Workaround to pull in packages needed to run with FEATURES=test. Portage-2.1.2 handles this internally, so don't set it in make.conf/package.use anymore