Inline Assembler bug fixes

[Walter Bright]

The inline assembler is a surprisingly compact piece of code for what it does, 
but is overly complex. It's also not used that much, so it has tended to be 
neglected, and bug reports have slowly accumulated for it. Some were 10 years old.

But, once one figures out how it works, might as well go through the bug list 
for iasm and see what can be done about them.

I'm happy to report that it has been whittled down to 3:

https://issues.dlang.org/show_bug.cgi?id=12635 - the description is a little 
vague and I can't determine what the issue actually is

https://issues.dlang.org/show_bug.cgi?id=12878 - this one is a bit complicated 
to fix, but fortunately isn't critical

https://issues.dlang.org/show_bug.cgi?id=15242 - an enhancement request, not a bug

The list:

https://issues.dlang.org/buglist.cgi?bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED&keywords=iasm&keywords_type=allwords&list_id=232881&query_format=advanced

My apologies to those who have been suffering waiting for these fixes.

Happy Assembling!