Allows to run regression tests in an outer/inner setup.

A '3 lines how to':
   perl tests/vg_regtest --outer-valgrind=../trunk_untouched/install/bin/valgrind --all
           (the outer results for a test xxx is in xxx.outer.log)
   To run with another tool (e.g. drd), add the argument --outer-tool=drd


Still to do/things to improve:

* Most (inner) tests are successful when running under an outer
  memcheck. Need to analyse the reasons of remaining failures.

* The memcheck annotations in m_mallocfree.c can be improved:
  - A superblock is marked 'undefined', it should rather be marked
    'no access'.
  - When a free block is splitted, the remaining free block is
    not made 'no access'. Instead, it is made 'undefined'.
      => this decreases the chance to find bugs.
      => this is not very efficient (e.g. the rest of a superblock
         is often marked undefined repetitively).
    Similarly, the free block created by VG_(arena_memalign)
    is marked 'undefined'. 'No access' would be preferrable.
  - mkInuseBlock marks the new block as undefined. This is probably
    not needed, as VALGRIND_MALLOCLIKE_BLOCK will do it already.
  - VG_(arena_malloc) should give the requested size to
    VALGRIND_MALLOCLIKE_BLOCK, not the malloc usable size,
    as this decreases the chance to find buffer overrun bugs.
    But giving the requested size is tricky (see comments in
    the code).

* need to do memcheck annotations in m_poolalloc.c
   so as to allow leak checking for pool allocated elements.

* vg_regtest.in
  - should analyse the results of the outer and should
    produce a separate result for the tests for which
    the outer detects an error or a memory leak or ...


Changes done:
   README_DEVELOPERS: document the new outer/inner features.
   manual-core.xml: document the new sim-hint no-inner-prefix
   tests/outer_inner.supp: new file, containing the suppressions for inner.
   vg_regtest.in: implement new args --outer-valgrind, --outer-tool, --outer-args.
   m_mallocfree.c: annotations for memcheck.
   m_libcprint.c: handle the new sim-hint no-inner-prefix
   m_main.c: do an (early) parse of --sim-hints




git-svn-id: svn://svn.valgrind.org/valgrind/trunk@12441

docs/xml/manual-core.xml

@@ -1646,6 +1646,15 @@ need to use these.</para>
           magic needed when the program being run is itself
           Valgrind.</para>
         </listitem>
+        <listitem>
+          <para><option>no-inner-prefix: </option> Disable printing
+          a prefix <option>&gt;</option> in front of each stdout or
+          stderr output line in an inner Valgrind being run by an
+          outer Valgrind. This is useful when running Valgrind
+          regression tests in an outer/inner setup. Note that the
+          prefix <option>&gt;</option> will always be printed in
+          front of the inner debug logging lines.</para>
+        </listitem>
         <listitem>
           <para><option>fuse-compatible: </option> Enable special
             handling for certain system calls that may block in a FUSE