PERF: Replace fill and copy with std alternatives

Use vcl_fill_n and vcl_copy, which are synonyms for std::fill_n
and std::copy, when possible in vnl_vector and vnl_matrix.

Filling vnl_vector using the std variant showed an increase in
performance with a factor between 1-10 for two different systems
(Win7 64bit VS2008 and Ubuntu Linux gcc 4.6.3), tested for short,
int, float and double, for array sizes between 1e2 and 1e7.
For relatively short sizes (<10) a decrease in performance was
noticed, but these operations are fast anyway.

Change-Id: I9e3284ebc1468c47eb84aee5f18165699a0ebbd6
COMP: Must reinterpret the pointers to match

complex<double> and double[2] types are compatible
memory layouts. The reinterpret_cast is used here
to make the "C" fftw libary compatible with the
c++ complex<double>.

Change-Id: I8eda7aa61d0dae4b16607cafcea6ec834d678a7b
Merge topic 'FFTWCopy'

f8af96e COMP: Must reinterpret the pointers to match
Merge topic 'FillArray'

04a394c PERF: Replace fill and copy with std alternatives