[trunk] Edit Text Styles dlg does not keep "Size follows space unit" setting

Setup: trunk rev. 4186 both under Win XP and Ubuntu 9.10

Steps:

1) Open (or create) a score whatsoever
2) Menu "Style | Edit text styles..."
3) change the "size follows Space unit" setting of any style
4) OK to close the dialogue box
5) Menu "Style | Edit text styles..." again

Result: the "size follows Space unit" setting changed in step 3) reverted to its original value

Notes:

1) The attached patch corrects function void TextStyleDialog::saveStyle(int n) in file textstyle.cpp, by commenting out a single statement (in line 85) which resets the style sizeIsSpatiumDependent parameter.

2) That statements was needed before the sizeIsSpatiumDependent parameter of TextStyle class was exposed in the UI; now it defeats any change made in th UI to this parameter.