doc: Small corrections in sec:languagetool.
Revise Markdown formatting.
Refactor: Rename global package table, move module references into own table.
Refactor: Pull ressources during module loading.

So far, all sub-modules had a `set_ressources' function which was used
to push shared ressources (variables) to a module by the module
loading chunk.  Now, shared ressources are made available during
module loading in a global variable `PKG_spelling'.  That is, modules
now pull ressources during initialisation.
Share reference to \AtBeginShipout function via global package table.

Don't pollute name space: avoid a global function.
Remove text output file EOL configuration.
Remove a wrong code point from table of default mappings.

LATIN CAPITAL LETTER SHARP S is not a valid character but a mistake.
doc: Revise table tab:cp-mapping.

Show sample glyphs in table listing default mappings.
doc: Adapt LanguageTool installation instructions to v2.1.
Improve LuaTeX 0.74 compatibility.

Explicitly require external modules.
Refactor: Revise identifiers of local references to unicode string functions.
Fix a bug in macro \spellingoutputlinelength.

The argument (a number) was erroneously converted to a string.
Fix a documentation error for macro \spellingoutputlinelength.
Reduce file system access during text file writing.

Paragraphs have been written line by line.  Now, a paragraph is
broken into lines in memory and then written at once.
Refactor: Rename some function local variables.
Refactor: Revise a loop logic.
Refactor: Rename main Lua file.
Refrain from using package ifthen in LaTeX .sty file.
Validate highlighting colour.
Refactor: Move XML error handling completely into XML handler.