Add additional dl_phdr_info fields

Previously, Bionic's dl_phdr_info only included the first four
dl_iterate_phdr fields. Several other libc's have these additional fields:

    unsigned long long dlpi_adds -- incremented when a library is loaded
    unsigned long long dlpi_subs -- incremented when a library is unloaded
    size_t dlpi_tls_modid -- TLS module ID
    void* dlpi_tls_data -- pointer to current thread's TLS block or NULL

These extra fields are also exposed by glibc, musl, and FreeBSD. The
unwinder in libgcc.a, linked into shipping Android DSOs, has a
PC->eh_frame cache that activates if dl_phdr_info has the dlpi_adds and
dlpi_subs fields (indicated at run-time by a sufficiently-large size
argument to the callback).

Bug: https://github.com/android-ndk/ndk/issues/1062
Test: bionic unit tests
Change-Id: I6f0bab548cf8c828af2ddab9eb01c5c6d70cd81f
diff --git a/libc/include/link.h b/libc/include/link.h
index 072f093..bd430f5 100644
--- a/libc/include/link.h
+++ b/libc/include/link.h
@@ -47,6 +47,12 @@
   const char* dlpi_name;
   const ElfW(Phdr)* dlpi_phdr;
   ElfW(Half) dlpi_phnum;
+
+  // These fields were added in Android R.
+  unsigned long long dlpi_adds;
+  unsigned long long dlpi_subs;
+  size_t dlpi_tls_modid;
+  void* dlpi_tls_data;
 };
 
 #if defined(__arm__)