android: Hoist Android blocks above linux blocks

Android implies linux, so it must be checked before linux.
android: Remove arch-blocks where possible

These structures don't depend on the architecture in bionic.
android: Add implementations for ARM and MIPS
android: in_port_t is available
android: Implement the features Android assumes
android: Add blocks for unsupported features

This prevents the `linux` blocks from defining things Android doesn't
support.
android: *stat64 are aliased to the non-64 variants
android: Define slong_t and ulong_t
android: Fix lseek and truncate
android: Use linux's rt.sections implementation
android: Remove duplicate FILE definition
android: Remove duplicate fpos_t
android: Bionic *does* implement getpw{nam,uid}_r
android: Implement the FD_* macros

Luckily, Linux's ABI compatibility saves us here.