[BRLTTY] brltty-6.0 build with alsa-1.1.9

[Jaroslav Skarvada]

Hi,

alsa-1.1.9 has been recently released. One of the change is drop of
the -I/usr/include/alsa from the alsa.pc [1], so the brltty sources
have to be changed to cope with it. Alsa upstream recommends using
#include <alsa/asoundlib.h> instead of #include <asoundlib.h> [2]

thanks & regards

Jaroslav

[1] https://alsa-project.org/wiki/Changes_v1.1.8_v1.1.9#Utils
[2] https://bugzilla.redhat.com/show_bug.cgi?id=1716389#c7