Gas64 rev

[SARG-FB]

I didn't use 'rebase --onto master start ' just 'rebase master' on gas64_rev branch. Hope no issue.

• fix sse41 test, before the asm test instruction was wrongly used.
• fix wrong optimization for xmmN registers.
• new optimizations canceling the above fix.
• some changes in asm_info() lines, typos fixes

[jayrm]

Thanks @SARG-FB . Looks like that should fix my mistake with the SSE41 tests in #261

Rebase is good. The PR is branched from current fbc/master, so that's perfect. It's nice to have the new changes on fbc/master as it makes picking commits for the fbc-1.07 branch very easy. Thank-you.

For the 4 sections beginning with ctx.roundfloat=true looks like there is enough duplicated code that it would be worth refactoring in to a private sub; something like private sub hEmitRoundFloat( ... ) or similar name. It would remove duplicate code and put the common task in one place -- if it needs to be changed in future, only have to change in one place rather than 4. Also makes the fbc executable a little smaller.

To update this PR, you can make the changes on your PC, and when ready push to your gas64_rev branch again. github will automatically update this PR and run travis-ci build tests again.