proposed solution for #1114
add line information into Tree.DocLink
fix #1111
improve test
ceylondoc #1869 allow parens in wiki links to functional declarations
Warning suppression:
* Add a flag to UsageWarning to mark a warning as "suppressed"
* Enumerate the warnings used by the typechecker
* When adding a warning to a Node, pass the enumerated warning type in addition to the message
* Add WarningSuppressionVisitor which will flag warnings which are suppressed
  by either being in some set of suppressed warnings passed to the PhasedUnit
  (i.e. configured from the command line) or which are suppressed in the
  source code by use of the new suppressWarnings annotation.

See ceylon/ceylon-compiler#1866
Fix typo.
Make unknown warning names in suppressWarnings into a warning itself suppressable via unknownWarning.
implement #1115
tests for #1115
update spec for #1115
set charPositionInLine for #1116
fix quotes in error message
eliminate unnecessary pointy brackets
fix problem reported by David Hagen in ML #1117
fix #1118
refresh intro chapter of spec and add more examples
Ret(*Args) type abbreviation #1121
print with new type abbreviation for Callable #1121
Put the keywords in the grammar file in alphabetical order