SyntaxConstructClassifier cancels running previous async computation before starting a new one

fix after rebase
update FsXaml to 0.9.4
Merge pull request #501 from vasily-kirichenko/FsXaml-0.9.4

update FsXaml to 0.9.4
HighlightUsageTagger uses AllowStaleResults.No instead of MatchingSource
Merge pull request #502 from vasily-kirichenko/fix-highligh-refs-does-not-appers-after-renaming

HighlightUsageTagger uses AllowStaleResults.No instead of MatchingSource
Merge pull request #496 from vasily-kirichenko/fix-wrong-current-line-coloring

SyntaxConstructClassifier cancels running previous async computation before starting a new one
Dispose leaked resources revealed by profiling

- Break references of ITextBuffer keeps to classifiers
- Cancel async runs and stop timer before disposing feature objects
Merge pull request #506 from dungpa/dispose-resources

Dispose leaked resources revealed by profiling
Add "Code Generation" option page
Minor cleanup
Refactor options pages
Create a new reg key for record stub generation
Merge pull request #508 from dungpa/code-gen-options

Add code generation options
Simplified Rename process

Moved to latest FsXaml and FSharp.ViewModule to improve error handling
(better tooltips/validation support).  This simplifies the code around
rename significantly and improves error reporting
Work on progress and cancel support in rename
More cleanup work on Rename
Cleanup on Rename, added progress

Rename now includes progress tracking, plus reporting during
initialization phases
Fixed accidental file checkin
Updated to address rename issues

Addresses issues raised by @dungpa relating to rename.
Updated to FSharp.ViewModule 0.9.6 to leverage new progress
functionality and simplify rename
Fixed undisposed CancellationTokenSource