Android tweaks

[joakim-noah]

Since Dan found the same problem with the ARM EH check on his RPi, disabling it for now, until it can be fixed. A lot of my remaining Android changes can be cherry-picked from this recent PR upstream.

Other than that, there's a workaround for a compile-time bug that shows up only when cross-compiling, a workaround for a strange issue with signal-handling only when running D in a shared library, three disabled test blocks (the latter two pass but may corrupt memory and cause problems only when run in the same process as other tests, which is also reproducible with dmd upstream), added a struct modifier because the clang EH header is different, reverted to GCed exceptions because of a codegen issue with emulated TLS on Android, and reworked the test runner to run all tests from a single process and so it can be called as a function by an Android apk. I did not submit these because most should be looked into and fixed, while some would just make existing code messier and be too specific.

[redstar]

Isn't the EH check fixed with #57 ? Otherwise LGTM.

[joakim-noah]

Yeah, looks like the subsequent PR #57 fixed the EH check, and it turns out I didn't need the additional logic in rt.sections_ldc. Reworking this PR, should have a new version up later.