Revert "[Sema] Diagnose tautological comparison with type's min/max values"

This reverts r315614,r315615,r315621,r315622
Breaks http://bb9.pgr.jp/#/builders/20/builds/59

/home/bb9/bootstrap-clang-libcxx-lld-i686-linux/llvm-project/libcxx/test/std/experimental/filesystem/fs.op.funcs/fs.op.last_write_time/last_write_time.pass.cpp:95:17: error: comparison 'long long' > 9223372036854775807 is always false [-Werror,-Wtautological-constant-compare]
    if (max_sec > Lim::max()) return false;
        ~~~~~~~ ^ ~~~~~~~~~~
/home/bb9/bootstrap-clang-libcxx-lld-i686-linux/llvm-project/libcxx/test/std/experimental/filesystem/fs.op.funcs/fs.op.last_write_time/last_write_time.pass.cpp:124:13: error: comparison 'long long' < -9223372036854775808 is always false [-Werror,-Wtautological-constant-compare]
    if (sec < Lim::min() || sec > Lim::max())   return false;
        ~~~ ^ ~~~~~~~~~~
/home/bb9/bootstrap-clang-libcxx-lld-i686-linux/llvm-project/libcxx/test/std/experimental/filesystem/fs.op.funcs/fs.op.last_write_time/last_write_time.pass.cpp:124:33: error: comparison 'long long' > 9223372036854775807 is always false [-Werror,-Wtautological-constant-compare]
    if (sec < Lim::min() || sec > Lim::max())   return false;
                            ~~~ ^ ~~~~~~~~~~
3 errors generated.
--

I'm not yet sure what is the proper fix.

llvm-svn: 315631