Fix the SKIP for android in t/run/fresh_perl.t
t/op/incfilter.t: Work around android only having an inbuilt echo
t/op/magic.t: Work around android only having an inbuilt pwd
Makefile.SH: on make test_prep, add $target/lib:$target/lib/auto to -env LD_LIBRARY_PATH=...
t/lib/warnings/pp_sys: Add skips in case telldir is not available
t/op/fork.t: Work around android only having an inbuilt echo
t/op/fork.t: Up the sleep time in a test to avoid timing issues
t/op/stat.t: use 'ls -l' on android, even if d_readlink is defined
t/op/sigdispatch.t: Increase timeout to avoid issues on slow processors
hints/linux-androideabi.sh: use randfunc=random and randbits=31
On Android, set $ENV{TMPDIR} on the tests for open($fh, undef)

This is primarily to get the tests working. open($fh, undef) calls
PerlIO_tmpfile(), which requires either /tmp to exist or $ENV{TMPDIR}
to be set.  In Android, neither of those is true.

A possible fix would be to have PerlIO_tmpfile() behave like File::Temp
and just try the cwd; the "real" fix would require calling java
at startup to get Context.getCacheDir.
perlio.c, PerlIO_tmpfile: Fall back to cwd if we have no /tmp or TMPDIR
Android hints: Detect stub functions and mark them as undefined.

Bionic implements several functions as stumps that simply warn
and return null, which leads to situations like this:

FIX ME! implement getprotobyname() bionic/libc/bionic/stubs.c:378

This commit introduces some probes for functions (getnetbyname,
getnetbyaddr, getmntent, getprotobyname, getprotobynumber, endpwent,
ttyname) that we use and are actually stubs in at least some
versions of Android.
If we find a stub, we pretend that the function is undefined, so
the above example becomes this:

Unsupported socket function "getprotobyname" called at -e line 1.

Note that this commit does not fix the modules that assume that
these functions are always available, so 'make test' still fails.
time64.h: Declare tm_zone as const under Android, but not if using C++
MakeMaker: Groundwork for d_libname_unique

Android's linker has some unusual behavior, in that it only uses
the basename of a library in its cache.  That means that, as far as
dlopen() is concerned, the libraries for Hash::Util and List::Util,
both of which are called Util.so, are the same.

This commit teaches ExtUtils::MM_Unix about d_libname_unique.  When
defined, it signals MakeMaker to rename the .so files to something
"unique" -- so for example, Hash/Util/Util.so becomes
Hash/Util/Perl_Hash_Util.so.
Teach XSLoader about d_libname_unique
Teach DynaLoader about d_libname_unique
android hints: Always define d_libname_unique
t/op/getpid.t: Silence undef warnings if getconf doesn't exist.

If a platform has getppid() but not getconf and we're building a
threaded perl, this file would've shown undef warnings, although
no tests were affected.
pod/perlport.pod: Note which functions are not available on Android