Fix code style, translate comments

Fix code style:
  * tabs->spaces
  * curly braces on same line
  * start preprocessor directives on first column, indent after leading
    hash-sign
  * improve readability of #ifdef switches in some places
Translate all German comments into English.
Fix code style, translate comments

Fix code style:
  * tabs->spaces
  * curly braces on same line
  * start preprocessor directives on first column, indent after leading
    hash-sign
Translate all German comments into English.