Invalid Free causes parsing the valgrind output to fail

[J. Frimmel]

If you have an invalid free, cargo-valgrind currently exits with an error. This is due to a changed Valgrind XML:

<error>
  <unique>...</unique>
  <tid>...</tid>
  <kind>InvalidFree</kind>
  <what>Invalid free() / delete / delete[] / realloc()</what>
  <stack>...</stack>
  <auxwhat>Address 0x8c2b840 is 0 bytes inside a block of size 16 free'd</auxwhat>
  <stack>...</stack>
  <auxwhat>Block was alloc'd at</auxwhat>
  <stack>...</stack>
</error>

Note the multiple stack fields.

To resolve this error the stack Error structure has to be changed, so that it provides a vector of Stacks.
Since the valgrind_xml module is not public, the change won't not API breaking.

[J. Frimmel]

At this point, the <auxwhat>-block should also be parsed and maybe presented to the user.

[J. Frimmel]

This requires to parse either a Resources struct in case of <xwhat> or a String in case of what. The same applies for auxwhat/xauxwhat.
Refer to the serde documentation on that topic.