What Math is used in Development Economics?
This does depend on whether you're looking to do applied econometric work, in which case statistics is definitely the way to go or something theoretical, in which case a good understanding in the maths you listed will go a long way. Of course it's always better if you understand both - since you're doing a master's in math, you should already be quite fluent with the math required, so I'd go with econometrics.

There's a growing amount of literature available, but if you have time to spare, I'd give the topics in Nafziger's "Economic Development" a glance: http://tabesh.edu.af/Books/economic/Economic%20Development.pdf