Delete the old pre-c++11 Thread implementation

[tgoyne]

This was a backport of std::thread to C++03 and we haven't needed it for a long time. std::thread doesn't expose set_name(), so that remains.

The other things in thread.hpp are still relevant for robust and process shared mutexes.

[coveralls-official]

Pull Request Test Coverage Report for Build thomas.goyne_351

Details

• 48 of 59 (81.36%) changed or added relevant lines in 6 files are covered.
• 40 unchanged lines in 13 files lost coverage.
• Overall coverage increased (+0.02%) to 90.819%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
test/test_lang_bind_helper.cpp	9	11	81.82%
test/test_thread.cpp	15	24	62.5%

Files with Coverage Reduction	New Missed Lines	%
src/realm/index_string.cpp	1	85.17%
src/realm/query_expression.hpp	1	93.81%
src/realm/sort_descriptor.cpp	1	94.06%
src/realm/uuid.cpp	1	98.48%
src/realm/mixed.cpp	2	86.46%
src/realm/sync/network/http.hpp	2	82.27%
src/realm/sync/noinst/server/server.cpp	2	74.11%
test/test_lang_bind_helper.cpp	2	93.2%
src/realm/sync/noinst/protocol_codec.hpp	3	73.5%
test/fuzz_group.cpp	5	45.77%

Totals
Change from base Build 2327:	0.02%
Covered Lines:	214642
Relevant Lines:	236341

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💛 - Coveralls