Log Message:
lv2: Update to 1.18.0

lv2 (1.18.0) stable;

  * Improve documentation.
  * Separate extended documentation from primary data.
  * core: Add lv2:Markdown datatype.
  * core: Deprecate lv2:reportsLatency.
  * patch: Fix incorrect type of patch:sequenceNumber.
  * port-groups: Remove incorrect type of pg:letterCode.
  * port-groups: Replace broken links with detailed Ambisonic channel
    descriptions.
  * state: Add state:freePath feature.
  * ui: Add ui:requestValue feature.
  * ui: Add ui:scaleFactor, ui:foregroundColor, and ui:backgroundColor
    properties.
  * ui: Deprecate ui:binary.
  * worker: Improve documentation.