replace tabs with 4 spaces.

[qPCR4vir]

a_group_impl.cpp

[cnjinhao]

Hi, what's the benefit of using 4 spaces?

[qPCR4vir]

Hi,
consistence. I have used MSVS (variable tabs, 4 spaces max) and it was OK to have tab for vertical alignment. So I have mixed everywhere tab and spaces. Now I use other editors too, and the tabs are no more interpreted as before, and the format is broken. GitHub is the worse (fixed 8 spaces). The examples are bad. But in VS are OK. The simple way to fix all is to replace all tab in VS with spaces. Here a simple example:
http://qpcr4vir.github.io/nana-doxy/html/d9/dda/example_listbox_8cpp-example.html
That is only in the examples, not in the nana code self.