Retinex-r4

• Fix compiling with Clang++.
• Upgrade MSVC to 2017.
• Fix identifier.
• Replace custom configure script with Meson build system.

Retinex-r3

Add new function retinex.MSRCR()----MSR with Color Restoration.
Fix incorrect result when lower_thr>0 or upper_thr>0.
Default parameters change: lower_thr=0.001, upper_thr=0.001.
Speed up about 15%.

Retinex-r2

MSRCP: Add option chroma_protect to attenuate chroma adjustment.
MSRCP: Intensity channel is calculated from average of R, G, B value
now, instead of weighted average.

Retinex-r1

Initial release