outlineCompiler: improve VORG table generation

[m4rc1e]

Whilst working on glyphsLib, I noticed that the VORG table generation is too greedy. If a glyph's vertical origin is the same as the table's default vertical origin, we don't need to add it.

Here's a quick before and after on a test font.

Current implementation

  <VORG>
    <majorVersion value="1"/>
    <minorVersion value="0"/>
    <defaultVertOriginY value="850"/>
    <numVertOriginYMetrics value="6"/>
    <VOriginRecord>
      <glyphName value=".notdef"/>
      <vOrigin value="850"/>
    </VOriginRecord>
    <VOriginRecord>
      <glyphName value="A"/>
      <vOrigin value="850"/>
    </VOriginRecord>
    <VOriginRecord>
      <glyphName value="B"/>
      <vOrigin value="850"/>
    </VOriginRecord>
    <VOriginRecord>
      <glyphName value="A.rotat"/>
      <vOrigin value="850"/>
    </VOriginRecord>
    <VOriginRecord>
      <glyphName value="A.half.rotat"/>
      <vOrigin value="850"/>
    </VOriginRecord>
    <VOriginRecord>
      <glyphName value="B.half.rotat"/>
      <vOrigin value="550"/>
    </VOriginRecord>
  </VORG>

This pr

  <VORG>
    <majorVersion value="1"/>
    <minorVersion value="0"/>
    <defaultVertOriginY value="850"/>
    <numVertOriginYMetrics value="1"/>
    <VOriginRecord>
      <glyphName value="B.half.rotat"/>
      <vOrigin value="550"/>
    </VOriginRecord>
  </VORG>

[m4rc1e]

@anthrotype friendly ping.

[anthrotype]

Thanks!