Add some Spacing Modifier Letters to charset_table
Add some Spacing Modifier Letters to charset_table

Of the Spacing Modifier Letters already present in the Tatoeba corpus,
  - ʻ (U+2BB MODIFIER LETTER TURNED COMMA) is used to write the Hawaiian
  Okina, so I added it.
  - ʼ (U+2BC MODIFIER LETTER APOSTROPHE) is used as a stand-in for a
  "regular" apostrophe, so I left it out.
  - ʿ (U+2BF MODIFIER LETTER LEFT HALF RING) is to transcribe the Arabic
  Ayin, so I added it.
  - ˀ (U+2C0 MODIFIER LETTER GLOTTAL STOP) is used to write the glottal
  stop in Cayuga, so I added it.
  - ˈ (U+2C8 MODIFIER LETTER VERTICAL LINE) and
  - ˌ (U+2CC MODIFIER LETTER LOW VERTICAL LINE) are used in IPA
  transcriptions to mark primary and secondary stress, which I think
  means they're better left out.
  - ː (U+2D0 MODIFIER LETTER TRIANGULAR COLON) is used to mark vowel
  length in Ngeq, so I added it.
Unicode Block: https://www.unicode.org/charts/PDF/U02B0.pdf

See issue #1970, section "Other Unsearchable Characters".

Tatoeba/tatoeba2,Tatoeba/tatoeba2,Tatoeba/tatoeba2,Tatoeba/tatoeba2,Tatoeba/tatoeba2