evas/cserve2: Merge Glyph_Data and mempool index

evas/cserve2: Merge Glyph_Data and mempool index

Glyphs were previously using 3 shared buffers, now reduce to 2:
- Memory pool (mempool) containing the glyph drawable data
- Index table (Shared_Index / array) containing only the
  indexes of the buffers in the mempool
- Glyph_Data table (array) containing the glyphs descriptors
  AS WELL as the buffer indexes.

So, we just merge the two index tables into one by using directly
objects of type Glyph_Data for the referencing of the mempool
buffers.