Vendor the old annotatedstring_optimize! from Base

It's about to be removed in an effort to make less assumptions about the
structuring of annotations, but it still makes sense to apply it here,
so we vendor the old version.

Author: tecosaur

src/styledmarkup.jl

@@ -641,6 +641,36 @@ function run_state_machine!(state::State)
     end
 end
 
+"""
+    annotatedstring_optimize!(str::AnnotatedString)
+
+Merge contiguous identical annotations in `str`.
+"""
+function annotatedstring_optimize!(s::AnnotatedString)
+    last_seen = Dict{Pair{Symbol, Any}, Int}()
+    i = 1
+    while i <= length(s.annotations)
+        region, keyval = s.annotations[i]
+        prev = get(last_seen, keyval, 0)
+        if prev > 0
+            lregion, _ = s.annotations[prev]
+            if last(lregion) + 1 == first(region)
+                s.annotations[prev] =
+                    setindex(s.annotations[prev],
+                             first(lregion):last(region),
+                             1)
+                deleteat!(s.annotations, i)
+            else
+                delete!(last_seen, keyval)
+            end
+        else
+            last_seen[keyval] = i
+            i += 1
+        end
+    end
+    s
+end
+
 """
     @styled_str -> AnnotatedString
 
@@ -740,7 +770,7 @@ macro styled_str(raw_content::String)
     elseif state.interpolated[]
         :(annotatedstring($(state.parts...)))
     else
-        annotatedstring(map(Base.Fix1(hygienic_eval, state), state.parts)...) |> Base.annotatedstring_optimize!
+        annotatedstring(map(Base.Fix1(hygienic_eval, state), state.parts)...) |> annotatedstring_optimize!
     end
 end
 
@@ -762,7 +792,7 @@ function styled(content::AbstractString)
     if !isempty(state.errors)
         throw(MalformedStylingMacro(state.content, state.errors))
     else
-        annotatedstring(state.parts...) |> Base.annotatedstring_optimize!
+        annotatedstring(state.parts...) |> annotatedstring_optimize!
     end
 end