gnu: Sync synopses with the Womb.

* gnu/packages/bazaar.scm (bazaar): Use synopsis from the Womb.
* gnu/packages/gv.scm (gv): Likewise.

gnu: gv: Move to a separate file.

* gnu/packages/ghostscript.scm (ghostscript): Remove libxext and libxt
  as inputs.
  (gv): Move to...
* gnu/packages/gv.scm (gv): ... here.  New file.
  (ghostscript/x): Variant of GHOSTSCRIPT with libxt and libxext as
  inputs.