input: use only one array for input sources

Removes some code duplication. Also restructure the input waiting code
a bit: split the select() loop into a input_wait_read() function. On
systems which do not have POSIX select(), this function has an alternate
implementation, which waits unconditionally.
input: invert negated boolean field
input: never wait if there are new events in the input queue

Move the reading loop from read_all_fd_events to read_events. If
got_new_events is set when calling read_events, don't actually wait
and set the timeout to 0.

(Note that not waiting is sort of transparent to the caller: the caller
is just supposed to execute the event loop again, and then it will
actually wait. mplayer.c handles this correctly.)

This might reduce latency with some input sources.
getch2-win: uncrustify
w32: update manifest for high DPI and Windows 8.1

Since Windows Vista, when running at 144 DPI or higher with composition
switched on, applications that don't declare themselves to be DPI aware
are stretched by the window manager, kind of like low resolution apps in
OSX.

To avoid this, declare DPI awareness in the manifest. Since mpv is
practically resolution independent this shouldn't cause any trouble. The
'True/PM' value declares per-monitor DPI awareness in Windows 8.1, so
that the mpv isn't shrunk when moved from a high DPI screen to one with
a lower DPI.

Also, avoid compatibility shims by declaring compatibility with all
Windows versions from Vista to 8.1 and add the missing uiAccess
attribute to the requestedExecutionLevel element.