The font cache in VCL returns different fonts for identical parameters,
which causes layout differences in Writer.

first we search the font with language 1054:
 debug: XXX 0x2103950   add to maFontNameList: TH SarabunPSK->waree
 p maFontNameList
 $9 = boost::unordered_map with 1 elements = {
   ["TH SarabunPSK"] = "waree"
 debug: XXX 0x2103950 found in maFontNameList: TH SarabunPSK->waree
in this very same invocation the "waree" is then rerouted to Deja Vu
(which can only be because it was called with language 1033):
 debug: XXX 0x2103950   add to maFontNameList: TH SarabunPSK->dejavusans
 p maFontNameList
 $11 = boost::unordered_map with 1 elements = {
   ["TH SarabunPSK"] = "dejavusans"
 }
 debug: XXX 0x2103950 found in maFontNameList: TH SarabunPSK->dejavusans

- the selection of different fonts happens in
  FcPreMatchSubstititution::FindFontSubstitute.
- we never get a direct cache hit from maFontInstanceList because there
  are some differences like WIDTH_DONTKNOW, and the maSearchName
- the first time a font is searched, it ends up in maFontInstanceList
- the second time a font is searched, it may end up in maFontNameList,
  which maps _only_ based on the name (appears to be an invalid optimization)
- once we have TH SarabunPSK->dejavusans in maFontNameList we can never
  select the other one because apparently dejavusans covers all languages

Change-Id: Ibd73de88d8fc3b6e1319eb34c261e55ea217a988
(cherry picked from commit bb51791a)