Merge pull request #1 from greenlion/master

update santec fork
fvrand definition
get_percentile()

* code reformatting
* definition
* restore group_concat_max_len
* validate v_percentile
disable()

* optimizations
* definition
* dont set max_sp_recursion_depth to invalid value, and restore old value
Merge pull request #4 from santec/master

get_percentile(), fvrand(), disable()