Inference failure in brfft on 0.7

From the Travis log (also seeing locally):
```
ERROR: LoadError: return type Array{Float64,2} does not match inferred return type Any
Stacktrace
[1] macro expansion at /home/travis/.julia/v0.7/FFTW/test/runtests.jl:335 [inlined]
[2] anonymous at ./:?
[3] include_relative(::Module, ::String) at ./loading.jl:464
[4] include(::Module, ::String) at ./sysimg.jl:14
[5] process_options(::Base.JLOptions) at ./client.jl:315
[6] _start() at ./client.jl:383
while loading /home/travis/.julia/v0.7/FFTW/test/runtests.jl, in expression starting on line 331
```
The line that's being hit is equivalent to `@inferred brfft(randn(10), 18)`. Oddly enough, running that from the REPL works fine for me.