Use std::string::data() instead of std::string::c_str().

Meaningless changes on boring day.
Utility: comment includes similarly to the rest of Directory.cpp.
Doc++
Provide also CORRADE_TARGET_{UNIX,WINDOWS}.

I'm tired of searching for proper platform-specific definitions all
the time. Also it seems that none of `__unix`, `unix` or `__unix__` is
defined on Apple's Clang. AARGH.
Use CORRADE_TARGET_{UNIX,WINDOWS} throughout the code.

Should fix issues with Directory (and subsequently also with
PluginManager) on OSX.
Utility: skip the test case, apparently OS X doesn't have /proc.

Need to find another non-seekable file for the test.
PluginManager: doc++

Hide PluginMetadata constructor, as it is used only internally.
doc: mention opening brace issues in Coding Style.
TestSuite: don't display file/line for skipped test cases.

The information is useless and adds only noise to test output as the
user doesn't need to trace why the test case was skipped, because the
skip was intentional.
Utility: make Utility::mkpath() no-op in Emscripten.
Utility: fix compiler warning on Emscripten.
Utility: doc++
Fix compilation on/for Windows.

Oh my. I really should test more.
Merge branch 'master' into compatibility

Conflicts:
	doc/corrade-cmake.dox