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: svn://svn.code.sf.net/p/libjpeg-turbo/code/trunk@1389 632fc199-4ca6-4c93-a231-07263d6284db
Rename the ARM64 assembly file to match the C file


git-svn-id: svn://svn.code.sf.net/p/libjpeg-turbo/code/trunk@1390 632fc199-4ca6-4c93-a231-07263d6284db