Try to autodetect and auto-enable compiler compatibility mode.

I'm sick of the neverending issue reports. Now the user doesn't need to
enable it in most cases (except when e.g. using Clang with
libstdc++-4.7, which can't be detected at all).
Don't display irrelevant compatibility messages.

When GCC46_COMPATIBILITY was passed explicitly, it printed out message
about autodetecting GCC 4.7, which is wrong.
package: remove explicit compatibility flags from Jenkins CI configs.
Utility: don't print useless output from resource compiler.

Print something only if compilation failed.
Utility: don't *ever* return nullptr on error in Resource::getRaw().

When the group is overriden and the file cannot be opened just fall
back to compiled-in one. We are asserting if the file does not exist,
so the user isn't expecting this at all.
Utility: fix misleading Resource::get() documentation.
PluginManager: fix weird behavior and crash of test under MSVC.

The internal static vars weren't unique when linking to both
CorradePluginManager and CorradePluginManagerTestLib. Not sure if this
is MSVC-only issue, maybe it affected also MinGW.
Disable another useless warning on MSVC.

Cherry-picked from ff691be03cdde9aa1284096d37f02865dc698eeb in
compatibility branch.
Disable "unreachable code" warnings on MSVC.

Every assertion has `return` after std::abort() to ensure that the code
will still compile when CORRADE_GRACEFUL_ASSERT is set. When it is not
set, the return really *is* unreachable, but we can't do anything about
that.
doc: fix order of arguments when building using CMake.
doc: no need to explicitly specify compatibility flags anymore.
doc: fix wording in building documentation.
Make GCC47_COMPATIBILITY message less misleading.

We are enabling it also for 4.8.0, because it doesn't have rvalue
references for *this yet.
Updated toolchains submodule with Android support.
Initial Android support.
Apparently Android is something like newlib.
Implicitly enable static build for Android.
doc: Android building documentation.
package: Android development PKGBUILDs.
Utility: added AndroidLogStreamBuffer class.

Work arounds the massive annoyance of stdout redirected to /dev/hell.