Lots of blocks had "llvm" or "nasm" syntax types but either weren't following
the syntax, or the syntax has changed (and sphinx hasn't keep up) or the type
doesn't even exist (nasm?).

Other documents had :options: what were invalid. I only removed those that had
warnings, and left the ones that didn't, in order to follow the principle of
least surprise.

This is like this for ages, but the buildbot is now failing on errors. It may
take a while to upgrade the buildbot's sphinx, if that's even possible, but
that shouldn't stop us from getting docs updates (which seem down for quite
a while).

Also, we're not losing any syntax highlight, since when it doesn't parse, it
doesn't colour. Ie. those blocks are not being highlighted anyway.

I'm trying to get all docs in one go, so that it's easy to revert later if we
do fix, or at least easy to know what's to fix.

llvm-svn: 276109

Here's a rough/first draft - it at least hits the actual textual IR
examples and some of the phrasing. It's probably worth a full pass over,
but I'm not sure how much these docs should reflect the strange
intermediate state we're in anyway.

Totally open to lots of review/feedback/suggestions.

llvm-svn: 231294

Some references to llvm-gcc were so crusty that I wasn't sure how to
proceed and so I've left them intact.

I also slipped in a quick peephole fix to use a :doc: link instead of
raw HTML link.

llvm-svn: 201619

Before we learned about :doc:, we used :ref: and put a dummy link at the
top of each page. Don't do that anymore.

This fixes PR14891 as a special case.

llvm-svn: 172162

llvm-svn: 169546

llvm-svn: 158858