test(buffer): add missing tests

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
test(hash): add missing tests

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
test(safe_arith): add unit tests

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
test(splay_tree): add missing test

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(splay_map): fix typo

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
test(library/rewriter/fo_match): clean up enable_trace
fix(script/demangle_cpptype): process line-by-line, instead of waiting for EOF