session info after a test case failure, allowing more direct inspection of
debugger session which leads to the test failure.

For a simple usage scenario:

[18:06:26] johnny:/Volumes/data/lldb/svn/trunk/test $ ./dotest.py -v . 2> ~/Developer/Log/lldbtest.log 

...

[18:14:43] johnny:/Volumes/data/lldb/svn/trunk/test $ ls -l .session-*
-rw-r--r--  1 johnny  admin  1359 Oct 14 18:06 .session-TestArrayTypes.ArrayTypesTestCase.test_with_dwarf_and_run_command
-rw-r--r--  1 johnny  admin  2054 Oct 14 18:07 .session-TestClassTypes.ClassTypesTestCase.test_with_dsym_and_expr_parser
-rw-r--r--  1 johnny  admin  2055 Oct 14 18:07 .session-TestClassTypes.ClassTypesTestCase.test_with_dwarf_and_expr_parser
-rw-r--r--  1 johnny  admin  1351 Oct 14 17:57 .session-TestClassTypes.ClassTypesTestCase.test_with_dwarf_and_run_command
[18:14:51] johnny:/Volumes/data/lldb/svn/trunk/test $ 

The test case which failed will have its recorded session info dumped to a
.session-* file in the current working directory.  For test suite using
relocated directory, expect to find the .session-* files there.

In this checkin, I also add @skip decorator to the two test methods in
test/foundation/TestObjCMethods.py as it looks like the test suite is
deadlocking when running the tests.  More investigations are needed.

llvm-svn: 116552