Fix several mathematical issues discovered in the ARM64 NEON code while running the extended regression tests introduced in r1267.  Specific comments can be found in the original patches: https://sourceforge.net/p/libjpeg-turbo/patches/64/
Fix several mathematical issues discovered in the ARM64 NEON code while running the extended regression tests introduced in r1267.  Specific comments can be found in the original patches:
https://sourceforge.net/p/libjpeg-turbo/patches/64/


git-svn-id: f4b8cdf16401e685066ebddaa7a36fa9f83fce1e@1389 632fc199-4ca6-4c93-a231-07263d6284db

bygreencn/mozjpeg,billychappell/mozjpeg,m-2k/mozjpeg,bygreencn/mozjpeg,ekandrot/mozjpeg,m-2k/mozjpeg,bygreencn/mozjpeg,zhoujianhanyu/mozjpeg,m-2k/mozjpeg,zhoujianhanyu/mozjpeg,billychappell/mozjpeg,ekandrot/mozjpeg,billychappell/mozjpeg,zhoujianhanyu/mozjpeg,ekandrot/mozjpeg,bygreencn/mozjpeg,m-2k/mozjpeg,ekandrot/mozjpeg,m-2k/mozjpeg,billychappell/mozjpeg,zhoujianhanyu/mozjpeg,zhoujianhanyu/mozjpeg,bygreencn/mozjpeg,billychappell/mozjpeg,ekandrot/mozjpeg