Windows build fixes.

Forgot to add exporter definition.
Utility: don't send extra newlines through NaClConsoleStreamBuffer.
Utility: verbose user-facing assert, test Unicode corner cases.
Enable GCC 4.7 compatibility for mingw32 build.

Arch's ming32-gcc is still at 4.7.
PluginManager: forgot this win-only code path while refactoring.
Utility: mingw32's GCC doesn't have std::to_string().
Utility: use nullptr instead of 0.
UseCorrade.cmake: remove old unneded cruft.

corrade_add_static() now takes one parameter less, removed dependent
functions which aren't used anywhere anymore, axed out also old and
irrelevant documentation.
UseCorrade.cmake: more cleanup.
UseCorrade.cmake: make corrade_add{,_static}_plugin() nearly the same.

It is now possible to conveniently install static plugins too using the
same syntax. It allows to do for example this:

    macro(add_plugin)
        if(NOT BUILD_STATIC)
            corrade_add_plugin(${ARGN})
        else()
            corrade_add_static_plugin(${ARGN})
        endif()
    endmacro()
Merge branch 'master' into compatibility

Conflicts:
	src/Utility/Resource.cpp
GCC 4.5 compatibility: no std::string::back() here.
Utility: don't send empty messages through NaClConsoleStreamBuffer.
Merge branch 'master' into compatibility

Conflicts:
	src/Utility/NaClStreamBuffer.cpp
Disable `-pedantic` for NaCl's GCC 4.4(.3).

It complains too much about comma at the end of enumeration list in
dependent projects even as that is perfectly valid code. My own 4.4.7
doesn't do that.