msvc: Update MSVC compiler flags.
msvc: Update MSVC compiler flags.

Disable couple warnings about int-float casting and const qualifiers
as they would require considerable work or are pointless to fix.

Also treat source files as UTF-8 as they contain non-ASCII characters.

AravisProject/aravis,AravisProject/aravis,AravisProject/aravis,AravisProject/aravis,AravisProject/aravis