Improve color highlighting of memory view.

Factor out and streamline code from the annotation highlighter
to create a list of colors suitable for highlighting and use that
in memory view.

Task-number: QTCREATORBUG-8250
Change-Id: Iefd408847897ddc98e3aecd6e4f084d1415b80c0
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/texteditor/syntaxhighlighter.h

@@ -66,6 +66,8 @@ public:
 
     void setExtraAdditionalFormats(const QTextBlock& block, const QList<QTextLayout::FormatRange> &formats);
 
+    static QList<QColor> generateColors(int n, const QColor &background);
+
 public Q_SLOTS:
     void rehighlight();
     void rehighlightBlock(const QTextBlock &block);