regression + bugfix: auto-tab-string

[Rune Zedeler]

In 2.10+2.11 the TabStaff auto-string-calculator won't use the first 
string:
http://lilypond.org/doc/v2.10/Documentation/user/lilypond/lily-c60b7608c6
The 2nd e is mussing on the tab.
This is a regression from 2.8:
http://lilypond.org/doc/v2.8/Documentation/user/lilypond/lily-1992430156.png

Patch attached

diff --git a/lily/tab-note-heads-engraver.cc b/lily/tab-note-heads-engraver.cc
index 0d56bb4..045e3f3 100644
--- a/lily/tab-note-heads-engraver.cc
+++ b/lily/tab-note-heads-engraver.cc
@@ -99,7 +99,7 @@ Tab_note_heads_engraver::process_music ()
          SCM scm_pitch = event->get_property ("pitch");
          int min_fret = robust_scm2int (get_property ("minimumFret"), 0);
          int start = (high_string_one) ? 1 : string_count;
-         int end = (high_string_one) ? string_count : 1;
+         int end = (high_string_one) ? string_count+1 : 0;
 
          int i = start;
          do