EXFAT bump version to 1.2.6 big update by @benpicco @mdcasey @lqs

All changes came from here

https://github.com/benpicco/linux_exfat-staging/commits/exfat
https://github.com/mdcasey/linux_exfat-staging/commits/mdcasey
https://github.com/dorimanx/exfat-nofuse/commit/d20735c6e81d05a8409ebd8326f3bdb3c16ac715
https://github.com/dorimanx/exfat-nofuse/commit/c8752270c08cad7486e502172ef6e1dc78f68085
https://github.com/dorimanx/exfat-nofuse/commit/e03f72516a65b73b376b74c547100a1c4da80022

HUGE thanks to developers that made such hard work on cleaning and fixing
the code for all of exfat users :)

Great work people!
EXFAT: little fix for DPRINT line to correct cde style.
remove __cplusplus stuff
remove fs_struct array and MAX_DRIVE limit
remove useless defines
for kernel version <= 3.3, linux/init.h doesnt include linux/types.h, so we include it here.
s32 -> int by @benpicco

https://github.com/benpicco/linux_exfat-staging/commit/2ffb5759a305652df17481d750454620f8c32bc6
Don't always show debug messages

CONFIG_EXFAT_DEBUG_MSG is always defined (either by Kconfig if on, or
exfat_config.h since 89d7aab6) so currently debugging messages are
always on.
Merge pull request #32 from ianw/debug

Don't always show debug messages
EXFAT: init sector value, and build in -O2
FIX Exfat function selection for Linux 3.13.1 main line.