Opposite condition with containers that are expressions

[pfultz2]

Currently, this test fails:

check("void f1(const std::string v[10]) { if(v[0].size() > 42) if(v[0].empty()) {}} ");
ASSERT_EQUALS("[test.cpp:1] -> [test.cpp:1]: (warning) Opposite inner 'if' condition leads to a dead code block.\n", errout.str());