It is useful to use the math expressions for the values in configuration.
This patch adds a simple expression evaluation routines (integer only).
The syntax is simplified unix shell (bash) style.
Examples:
$[1 + 1]
$[$[2 + 2] / $var1]
$[0xa0 | 0x05]
As a bonus, the variable substitutions were more abstracted.
The function snd_config_expand_custom() was introduced to be used
for example in the topology pre-precessor.
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
