Merge #599: Switch x86_64 asm to use "i" instead of "n" for immediate values.

Merge #599: Switch x86_64 asm to use "i" instead of "n" for immediate values.

d58bc93 Switch x86_64 asm to use "i" instead of "n" for immediate values. (Gregory Maxwell)

Pull request description:

  The constraint "n" is a more obscure setting which is needed for
   special cases that don't apply to our use.

  Use of "n" exposed some bugs in pre-release versions of clang.
  This fixes #594

Tree-SHA512: 1ffba02aa6bfcd0b6f731196e5d007f4ddb0f03f53b30a2633f0e376578cf7f828570579502f2de721dcda8034fd8e7bea822542bf36032d98ef802b4cf27725