Made all header files to have LABWC_ prefix in include guard identifers.
Converted from __LABWC_ in 35 include/ files.
Converted from __LAB_ in 5 include/ files.
Added LABWC prefix to 3 include/ files.
Added include guards to 3 include/ files.
The double underscores were removed since according to C standard
those "are always reserved for any use".
Expanding shell variables, including tilde, enables the following type
of keybind:
<keyboard>
<keybind key="XF86AudioMute">
<action name="Execute">
<command>bash ~/mute-script.sh</command>
</action>
</keybind>
</keyboard>
Fixes issue #32
