build issues re -Wimplicit-function-declaration
portage repeats and lists warnings for convenience at the end of an install

``` python
>>> Completed installing pandas-0.14.1 into /mnt/gen2/TmpDir/portage/dev-python/pandas-0.14.1/image/

strip: x86_64-pc-linux-gnu-strip --strip-unneeded -R .comment -R .GCC.command.line -R .note.gnu.gold-version
   usr/lib64/python2.7/site-packages/pandas/algos.so
   usr/lib64/python2.7/site-packages/pandas/index.so
   usr/lib64/python2.7/site-packages/pandas/tslib.so
   usr/lib64/python2.7/site-packages/pandas/lib.so
   usr/lib64/python2.7/site-packages/pandas/parser.so
   usr/lib64/python2.7/site-packages/pandas/hashtable.so
   usr/lib64/python2.7/site-packages/pandas/_sparse.so
   usr/lib64/python2.7/site-packages/pandas/_testing.so
   usr/lib64/python2.7/site-packages/pandas/msgpack.so
   usr/lib64/python2.7/site-packages/pandas/json.so

 * QA Notice: Package triggers severe warnings which indicate that it
 *            may exhibit random runtime failures.
 * pandas/tslib.c:17485:5: warning: implicit declaration of function ‘cmp_pandas_datetimestruct’ [-Wimplicit-function-declaration]
 * pandas/src/ujson/python/objToJSON.c:1765:5: warning: implicit declaration of function ‘encode’ [-Wimplicit-function-declaration]

 * Please do not file a Gentoo bug and instead report the above QA
 * issues directly to the upstream developers of this software.
 * Homepage: http://pandas.sourceforge.net/
```

Do you require any further information?
