SF bug #1296433 (Expat bug #1515266): Unchecked calls to character data
handler would cause a segfault.  This merges in Expat's lib/xmlparse.c
revisions 1.154 and 1.155, which fix this and a closely related problem
(the later does not affect Python).

Moved the crasher test to the tests for xml.parsers.expat.
3 files changed