C target language UT linkage bug fixed

Changes included:
* debugging of (the prototype) def. file metadata parser
  (formal placeholders substitutions)
* Proper make error propagation in the generated code
* Environment settings fixed
* UT script permissions fixed
changelog.sh: HTML output formatting fixed

Simple indentation by one space weas not enough to prevent
unwanted effects of characters (or sequences of characters)
that have special meaning in asciidoc.

The HTML representation was therefore changed to prevent that:
* preformatted blocks are used for the descriptions
* Boxes were replaced by 4-th level sections
  (not to use box nesting)
#changelog