Fix issue 12962 - use isainfo on Solaris to determine model
Fix issue 12965 - DMD sets ELFOSABI to ELFOSABI_LINUX on all systems
Fixed comment alignment; added #error for undefined ELF ABIs
Merge pull request #3686 from jasonbking/issue_12962

Fix issue 12962 - use isainfo on Solaris to determine model
Merge pull request #3687 from jasonbking/osabi

Fix issue 12965 - DMD sets ELFOSABI to ELFOSABI_LINUX on all systems
Fix Linux/64 compile error.
Merge pull request #3691 from quickfur/missing_endif

Fix Linux/64 compile error introduced by pull #1296
Fix issue 12968 - Incorrect codgen for xchg with R8
Merge pull request #3690 from Orvid/issue12968

Fix issue 12968 - incorrect codegen