Move tilegx, tilepro, and linux-generic from ports to libc.

I've moved the TILE-Gx and TILEPro ports to the main sysdeps hierarchy,
along with the linux-generic ports infrastructure.  Beyond the README
update, the move was just

    git mv ports/sysdeps/tile sysdeps/tile
    git mv ports/sysdeps/unix/sysv/linux/tile \
      sysdeps/unix/sysv/linux/tile
    git mv ports/sysdeps/unix/sysv/linux/generic \
      sysdeps/unix/sysv/linux/generic

I updated the relevant ChangeLogs along the lines of the ARM move
in commit c6bfe5c4d75 and tested the 64-bit tilegx build to confirm that
there were no changes in "objdump -dr" output in the shared objects.

1 files changed, 6 insertions, 0 deletions

diff --git a/sysdeps/tile/Versions b/sysdeps/tile/Versions
new file mode 100644
index 0000000000..b275d7ff3b
--- /dev/null
+++ b/sysdeps/tile/Versions
@@ -0,0 +1,6 @@
+libc {
+  GLIBC_2.12 {
+    # name requested by gcc community.
+    __mcount;
+  }
+}