[Common/x86] Add some documentation for X86_32_PICASM helpers
[Common/x86] Add some documentation for X86_32_PICASM helpers

mstorsjo/openh264,mstorsjo/openh264,shihuade/openh264,cisco/openh264,mstorsjo/openh264,GuangweiWang/openh264,sijchen/openh264,mstorsjo/openh264,sijchen/openh264,GuangweiWang/openh264,sijchen/openh264,ruil2/openh264,ruil2/openh264,sijchen/openh264,GuangweiWang/openh264,mstorsjo/openh264,cisco/openh264,ruil2/openh264,cisco/openh264,shihuade/openh264,shihuade/openh264,mstorsjo/openh264,ruil2/openh264,sijchen/openh264,cisco/openh264,GuangweiWang/openh264,cisco/openh264,shihuade/openh264,GuangweiWang/openh264,ruil2/openh264,GuangweiWang/openh264,GuangweiWang/openh264,shihuade/openh264,mstorsjo/openh264,ruil2/openh264,sijchen/openh264,cisco/openh264,ruil2/openh264,cisco/openh264,shihuade/openh264,sijchen/openh264,shihuade/openh264