[trunk] dot for note longer than whole has wrong value

Setup: trunk SVN rev. 4623; Qt lib 4.7.3; Ubuntu 11.04

Steps:

1) Open or create any score
2) In note enter mode, enter a dotted brevis or a dotted longa:

Result: the note actually inserted in the score is a brevis+minima or longa+minima, instead of brevis+semibrevis or longa+brevis.

Patch:

The attached patch corrects the function Duration::fraction() in file durationtype.cpp, replacing line 383:
      a += Fraction(1, n);
with:
      a += Fraction(z, n);