libc: Fix alphasort() signature (and implementation).

The declaration for alphasort() in <dirent.h> used the deprecated:

  int alphasort(const void*, const void*);

while both Posix and GLibc use instead:

  int alphasort(const struct dirent** a, const struct dirent** b);


This patch does the following:

- Update the declaration to match Posix/GLibc
- Get rid of the upstream BSD code which isn't compatible with the new
- Implement a new trivial alphasort() with the right signature, and
  ensure that it uses strcoll() instead of strcmp().
- Remove Bionic-specific #ifdef .. #else .. #endif block in
  dirent_test.cpp which uses alphasort().

Even through strcoll() currently uses strcmp(), this does the right
thing in the case where we decide to update strcoll() to properly
implement locale-specific ordered comparison.

Change-Id: I4fd45604d8a940aaf2eb0ecd7d73e2f11c9bca96
5 files changed