extend core classes syntax group
improve symbol syntax
syntax: add printf functions
further syntax tweaks
syntax: fix preproc directives
finally fix those regions
enable syntax based folding
fix those symbols
set commentstring appropriately
improvement of commenting behavior
make ftplugin undo-able
fix namespaces and precompiler directives
reduce probability of incorrect XML comment matching

XML documentation comments are now only shown in single line comments
starting with three slashes '///'
fix the XML doc comment regions
add 'nowarn' directive keyword
show F# interactive error on invocation only
improve fsSymbol regex
fix valid keywords
syntax: add support for mutually recursive functions
rename syntax groups from fs* to fsharp*

This naming pattern enables improved usability for vim's syntax based
completion.