#6 Spectrum views enhancement & small eq fixes

[rdoursenaud]

This small patch against current CVS fixes a few annoyances I got for a long time with JAMin.

1) Relabeled geq sliders with correct frequency.

2) Correctly calculate tooltip frequency from new geq labels.

3) Correct spectrum view frequency labels.

4) Accurate frequency display in spectrum view (fixes bug #1736245).

5) Same on hdeq display. As a side effect, removed rising/decaying display. Plan to reintroduce it in a more flexible manner later.

6) Fix for "pen tool" measurement induced by new hdeq display.

Accuracy of spectrum displays and measurements has been tested with the excellent japa & jaaa as sound generators and display references.
This is my first C code ever. Please review, comment or commit ;)

[rdoursenaud]

Spectrum views enhancement & small eq fixes