TestSuite: compare files as binary.

Cost me two hours to investigate why apparently working code was failing
the test with missing CR character on MSVC.
Utility: removed unused variable.

Don't know why this was here and why no compiler complained about that.
Utility: mark test files as binary to avoid Git CRLF conversions.

Resource tests should pass again on MSVC.
Utility: test scientific floating-point string output defensively.

The number of exponent digits is unspecified in the standard, so MSVC
has three digits while GCC and Clang has two digits.
UseCorrade.cmake: honor CMAKE_CFG_INTDIR in corrade_add_plugin().

MSVC and XCode puts the binaries into configuration-based subdirectory
of CMAKE_CURRENT_BINARY_DIR, thus we need to copy the plugin
configuration file also to the subdir and open plugin manager in
CMAKE_INTDIR subdirectory to have the plugins found properly.