ENH: Bump FFTW to 3.3.3.

Also use midas3.kitware.com to host the tarball and improve download
reliability.

Change-Id: Icae54c78687319f55d9a3dd41bc28eeff53f16dd
STYLE: Coverity 1103107-1103116: Logically dead code

Change-Id: I3bfe33d0d563a09c0cfc5c3f019b6c18b25d56dd
Merge topic 'cov_1103107'

3e4187fa STYLE: Coverity 1103107-1103116: Logically dead code
Merge topic 'fftw-midas2'

7a4fb5b4 ENH: Bump FFTW to 3.3.3.