sys_sdl_win.c: Sys_SetDPIAware: call SetProcessDPIAwareness / SetProcessDPIAware

git-svn-id: svn://svn.code.sf.net/p/quakespasm/code/trunk/quakespasm@1119 af15c1b1-3010-417e-b628-4374ebc0bcbd
readme: remove section about High-DPI workaround as we've got a proper fix now

git-svn-id: svn://svn.code.sf.net/p/quakespasm/code/trunk/quakespasm@1120 af15c1b1-3010-417e-b628-4374ebc0bcbd
sys_sdl_win: Sys_SetDPIAware: only call GetProcAddress on a non-NULL library handle

git-svn-id: svn://svn.code.sf.net/p/quakespasm/code/trunk/quakespasm@1121 af15c1b1-3010-417e-b628-4374ebc0bcbd
readme: add a note that the Windows DPI scaling issues are fixed

git-svn-id: svn://svn.code.sf.net/p/quakespasm/code/trunk/quakespasm@1122 af15c1b1-3010-417e-b628-4374ebc0bcbd