Fix -var-create and -var-update (MI)

Summary:
This patch includes:
* Fix -var-create command for global/static variables
* Fix -var-update command: remove m_strValueName/m_eVarInfoFormat/m_bValueChanged{Array,Composite,Normal}Type;  clean CMICmdCmdVarUpdate::Execute and CMICmdCmdVarUpdate::Acknowledge; improve CMICmdCmdVarUpdate::MIFormResponse; Complete the value after -var-create using the CMICmdCmdVarCreate::CompleteSBValue to get SBValue::GetValueDidChange work.
* Add non-constant version of CMICmnLLDBDebugSessionInfoVarObj::GetValue
* Add MiVarTestCase.test_lldbmi_var_update test

All tests pass on OS X.

Reviewers: abidh, emaste, clayborg

Reviewed By: clayborg

Subscribers: lldb-commits, emaste, clayborg, abidh

Differential Revision: http://reviews.llvm.org/D8110

llvm-svn: 231525