COMP: Suppress linker warning from fftw external project

This is yet another attempt to suppress the following warnings on the
dashboard:

Change-Id: Ibb4ad1d1a19768630bd849969d7222362271ecfa
libtool: install: warning: relinking `libfftw3f_threads.la'
libtool: install: warning: relinking `libfftw3_threads.la'
COMP: Add DoubleConversion merge from upstream documentation

DoubleConversion is a Google project, managed at this repository
https://code.google.com/p/double-conversion/

The txt files describe the procedure to merge upstream changes.
It's based on the work done for VNL; see
Modules/ThirdParty/VNL/src/README-ITK.txt

Change-Id: Ic1e958cfab2e7f1b057609a47946208540e6acd3
BUG: Don't allocate empty names in Get I/O Names methods

Pre-allocate the vector of names, and don't initialize as an array of
empty elements. Previously, the first half of the array of names was
empty strings.

Change-Id: Ic25989f2c41147e2f8eaa3cfe3128707c6b73715
COMP: Bumped up minimum required CMake version

- Minimum version for any system is 2.8.4

- Minimum version for Windows is 2.8.8

- Minimum version for systems without /dev/urandom is 2.8.5

Change-Id: Ide6335732ef1218b953b5eb8ad59e40765b681f0
Merge topic 'AddDoubleConversionUpstreamMergeDocs'

d1e8446 COMP: Add DoubleConversion merge from upstream documentation
Merge topic 'FixGetIONames'

5500e93 BUG: Don't allocate empty names in Get I/O Names methods
Merge topic 'SuppressFFTWlibtoolWarning'

81cec44 COMP: Suppress linker warning from fftw external project
Merge topic 'CMakeMinimumVersion'

e539b94 COMP: Bumped up minimum required CMake version