test infrastructure for cufft, clfft, fftw added.

[tdd11235813]

Added tests for cufft, clfft and fftw.

• gearshifft executes 64-FFTs in all fashions
  • return value of master test suite is now propagated to the system, so failed tests lead to non-zero return value of the main function
• some non-gearshifft tests to check FFT libraries directly
• cmake files are reorganized
  • using set(CMAKE_CXX_STANDARD 14) as of the cmake 3.1 requirement

minor fftw client fix

• fftw client now checks failed thread initialization

Example of a test output:

$ make test
Running tests...
Test project /<snip>/gearshifft/release
    Start 1: gearshifft_cufft
1/7 Test #1: gearshifft_cufft .................   Passed    1.89 sec
    Start 2: gearshifft_clfft
2/7 Test #2: gearshifft_clfft .................   Passed    1.49 sec
    Start 3: gearshifft_fftw
3/7 Test #3: gearshifft_fftw ..................   Passed   12.16 sec
    Start 4: test_cufft
4/7 Test #4: test_cufft .......................   Passed    1.46 sec
    Start 5: test_clfft
5/7 Test #5: test_clfft .......................   Passed    0.99 sec
    Start 6: test_clfft_global_fixture
6/7 Test #6: test_clfft_global_fixture ........   Passed    0.55 sec
    Start 7: test_fftw
7/7 Test #7: test_fftw ........................   Passed    0.04 sec

100% tests passed, 0 tests failed out of 7

Total Test time (real) =  18.66 sec

[tdd11235813]

added one commit:

+2 clfft tests. integrates comments by @ax3l

• adds 2D C2C outplace and <float,double> 1D R2C inplace clFFT test
• see ax3l's review of PR #110