Bug#717533: ratpoints: FTBFS: error: You need the GMP headers to compile ratpoints

[Aaron M. Ucko]

Source: ratpoints
Version: 2.1.3+dfsg-1
Severity: serious
Justification: fails to build from source

Builds of ratpoints in minimal environments (as on the autobuilders)
have been failing:

  checking for GMP includes in /usr/include/... not found
  configure: error: You need the GMP headers to compile ratpoints

Please declare a build dependency on libgmp3-dev and confirm with
pbuilder or the like that you haven't missed any others.

Thanks!