The xfrac package is the "state of the art" for "split-level" (nice) fractions.
Character replacements look consistent, scale properly and fit in the line.
Fixes#5220.
Test unicodesymbols for most supported input encodings with Kornel's addition to ctests.
Add required "forces" to unicodesymbols:
* utf8x does not support all characters supported by LyX
* several 8-bit encodings map characters to math-mode commands - force replacement in text-mode so that LyX can wrap them in \\ensuremath.
Fix a misalignment (wrong replacements) in the Cyrillic Unicode block.
Use \\mathscr for Mathematical Script characters in Mathematical Alphanumeric Characters (in line with the characters in other unicode blocks.
Rename the directory for test samples "export/latex/Unicode-characters" to "export/latex/unicodesymbols". This matches the purpose to test the lib/unicodesymbols file.
First run of Kornels patch for tests with all input encodings in lib/encodings.
Remove redundant sample files - keep only one sample and change the input encoding in the test script.
Put remaining failing test in "unreliableTests" for later sorting...
Move them to a subdir, ignore this subdir for other tests.
Dedicated test samples for LaTeX-specific problems don't give additional value if tested for loading, conversion, or other exports.
