Add VS2013 support.
include/qt/fp.h: guard define.

This fixes a redefinition warning with VS2013.
Fix compilation error with VS2013.
Update Compilation.txt.
Merge pull request #117 from XhmikosR/vs2013

VS2013 support
common.props: Specify _WIN32_WINNT and _WIN32_IE too.
AboutDlg.cpp: Adjust the number of slashes based on the build.
Compress toolbarw7.png.