v1.2.12

Release v1.2.12

Core
 - Release v1.2.12
 - hcontrol,mixer: improve callback GIL state handling
 - setup.py: fix symlinks for test programs for python 3
 - setup.py: licence -> license
pyalsa.alsahcontrol module
 - hcontrol,mixer: improve callback GIL state handling
pyalsa.alsamixer module
 - hcontrol,mixer: improve callback GIL state handling
pyalsa.alsaseq module
 - alsaseq: fix seg. fault when accessing `ConstantObject` extra

Signed-off-by: Jaroslav Kysela <perex@perex.cz>