[mathtext] isolate from ROOT and sync with upstream

[ferdymercury]

Variant of #22462 but upgrading to latest version (2016) and decoupling from ROOT libs

It's basically the version of @yslai at https://github.com/yslai/mathtext/tree/master/src/libmathtext with just a few patches on top to solve compilation errors.

PDF output might be potentially achievable since newer version of which has fontembedpdf.cc file

[github-actions]

Test Results

    22 files      22 suites   3d 15h 6m 4s ⏱️
 3 862 tests  3 854 ✅   0 💤  8 ❌
77 198 runs  76 968 ✅ 217 💤 13 ❌

For more details on these failures, see this check.

Results for commit 1369aed.

♻️ This comment has been updated with latest results.

[ferdymercury]

@bellenot does the Windows memmem backup implementation make sense to you? I am not sure if that is the reason for the CI failure

[bellenot]

@bellenot does the Windows memmem backup implementation make sense to you? I am not sure if that is the reason for the CI failure

I'll have to check carefully to see what it does. BTW, did you also check this one ? https://github.com/git/git/blob/master/compat/memmem.c

[bellenot]

@ferdymercury here are the errors:

  C:\ROOT-CI\src\builtins\libmathtext\fontembed.cc:644: error: access out of bound in table directory
  C:\ROOT-CI\src\builtins\libmathtext\fontembed.cc:1688: error: OTF CFF font is missing required tables
  C:\ROOT-CI\src\builtins\libmathtext\fontembedps.cc:401:
  C:\ROOT-CI\src\graf2d\postscript\src\TPostScript.cxx:1523:
  ...

and:

  Processing C:/ROOT-CI/src/tutorials/visualisation/graphics/tmathtext.C...
  Info in <TCanvas::Print>: png file c1.png has been created
  C:\ROOT-CI\src\builtins\libmathtext\fontembed.cc:644: error: access out of bound in table directory
  C:\ROOT-CI\src\builtins\libmathtext\fontembed.cc:1688: error: OTF CFF font is missing required tables
  C:\ROOT-CI\src\builtins\libmathtext\fontembedps.cc:401:
  C:\ROOT-CI\src\graf2d\postscript\src\TPostScript.cxx:1523:
  Error in <TPostScript::FontEmbed>: failed to embed font 4 (filename 'C:\ROOT-CI\build\fonts\FreeSans.otf')
  C:\ROOT-CI\src\builtins\libmathtext\fontembed.cc:644: error: access out of bound in table directory
  C:\ROOT-CI\src\builtins\libmathtext\fontembed.cc:1688: error: OTF CFF font is missing required tables
  C:\ROOT-CI\src\builtins\libmathtext\fontembedps.cc:401:
  C:\ROOT-CI\src\graf2d\postscript\src\TPostScript.cxx:1523:
  ...