The solver code is apparently quite unreliable, failures such as:

File "/sc/qa/uitest/goalSeek/tdf37341.py", line 43, in test_tdf37341_goalSeek
    self.assertEqual(get_cell_by_position(document, 0, 4, 6).getValue(), 12879.147)
AssertionError: 11751.688982 != 12879.147

or crash on shutdown:

0  in std::unique_ptr<SfxAppData_Impl, std::default_delete<SfxAppData_Impl> >::get() const (this=0x28) at /usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/bits/unique_ptr.h:234
1  in std::unique_ptr<SfxAppData_Impl, std::default_delete<SfxAppData_Impl> >::operator->() const (this=0x28) at /usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/bits/unique_ptr.h:228
2  in SfxApplication::GetObjectShells_Impl() const (this=0x0) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/sfx2/source/appl/app.cxx:403
3  in SfxObjectShell::GetFirst(std::function<bool (SfxObjectShell const*)> const&, bool) (isObjectShell=..., bOnlyVisible=true) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/sfx2/source/doc/objxtor.cxx:450
   41bef610: {maData = std::__debug::vector of length -417946822263704711, capacity -485587501518907230 = {<error reading variable>
4  in ScFormulaReferenceHelper::enableInput(bool) (bEnable=true) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/sc/source/ui/miscdlgs/anyrefdg.cxx:94
5  in ScFormulaReferenceHelper::dispose() (this=0x32076e0) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/sc/source/ui/miscdlgs/anyrefdg.cxx:78
   2076c0
6  in ScRefHandler::disposeRefHandler() (this=0x32076c0) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/sc/source/ui/miscdlgs/anyrefdg.cxx:823
7  in ScRefHandler::~ScRefHandler() (this=0x32076c0) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/sc/source/ui/miscdlgs/anyrefdg.cxx:815
8  in ScRefHdlrImplBase<SfxModelessDialog, true>::~ScRefHdlrImplBase() (this=0x3207390, vtt=0x2b8443074d78 <VTT for ScSolverDlg+24>) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/sc/source/ui/inc/anyrefdg.hxx:198
9  in ScRefHdlrImpl<ScAnyRefDlg, SfxModelessDialog, true>::~ScRefHdlrImpl() (this=0x3207390, vtt=0x2b8443074d70 <VTT for ScSolverDlg+16>) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/sc/source/ui/inc/anyrefdg.hxx:229
10 in ScAnyRefDlg::~ScAnyRefDlg() (this=0x3207390, vtt=0x2b8443074d68 <VTT for ScSolverDlg+8>) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/sc/source/ui/inc/anyrefdg.hxx:232
11 in ScSolverDlg::~ScSolverDlg() (this=0x3207390, vtt=0x2b8443074d60 <VTT for ScSolverDlg>) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/sc/source/ui/miscdlgs/solvrdlg.cxx:80
12 in ScSolverDlg::~ScSolverDlg() (this=0x3207390) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/sc/source/ui/miscdlgs/solvrdlg.cxx:78
13 in ScSolverDlg::~ScSolverDlg() (this=0x3207390) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/sc/source/ui/miscdlgs/solvrdlg.cxx:78
14 in VclReferenceBase::release() const (this=0x3207928) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/include/vcl/vclreferencebase.hxx:45
15 in rtl::Reference<vcl::Window>::~Reference() (this=0x2fb0bb0) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/include/rtl/ref.hxx:90
16 in VclPtr<vcl::Window>::~VclPtr() (this=0x2fb0ba8) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/include/vcl/vclptr.hxx:117
17 in WindowUIObject::~WindowUIObject() (this=0x2fb0ba0) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/include/vcl/uitest/uiobject.hxx:102
18 in DialogUIObject::~DialogUIObject() (this=0x2fb0ba0) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/vcl/source/uitest/uiobject.cxx:592
19 in DialogUIObject::~DialogUIObject() (this=0x2fb0ba0) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/vcl/source/uitest/uiobject.cxx:591
20 in std::default_delete<UIObject>::operator()(UIObject*) const (this=0x32543d8, __ptr=0x2fb0ba0) at /usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/bits/unique_ptr.h:67
21 in std::unique_ptr<UIObject, std::default_delete<UIObject> >::reset(UIObject*) (this=0x32543d8, __p=0x2fb0ba0) at /usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/bits/unique_ptr.h:262
22 in UIObjectUnoObj::~UIObjectUnoObj() (this=0x3254370) at /home/tdf/lode/jenkins/workspace/lo_gerrit/Config/linux_clang_dbgutil_64/vcl/source/uitest

Change-Id: I350ad562bbea945711de6e69e82f59ed728ab605