README: Update

Update link from i9100/P thread to main development thread on XDA.
optimize read file to buffer function to get len bytes read
fix fread returns unsigned instead of int
add read size progress bar during md5 sum computing
fix md5sum state color was reset to default after a few seconds
ensure path is mounted before computing md5 operations
remove tabs
readability
update 6.21.2
update for SAMSUNG GT-I8262
use different USB PIDs for adb and adb+ums modes

Commit ad054c684524962eae3269c1d807dc60e8bca1ec made it so that
the same VID/PID pair was used for both adb and composite adb+ums
modes, which prevents the installation of drivers in Windows so that
either mode can be supported.

This uses the original VID/PID pair (18d1/d001) for adb+ums and
uses 18d1/d002 for adb.

Change-Id: I190c821995b7fe9e8177354aec70bd02c114d122
RECOVERY_VERSION: bring inline with CyanogenMod's string

Fixes makerecoveries.sh printing an empty variable:
https://github.com/CyanogenMod/android_build/blob/cm-11.0/tools/device/makerecoveries.sh
new devices
fix MTK C flags could not be correctly passed
no need to mount twice
formatting
fix compiling for Advanced Edition
const correctness
libtouch_gui 1.08
try to fix random crash on some devices during md5 checks
6.21.9
add Xperia S
libtouch_gui meaningless update