Incorrect parsing after importing xmlsec

[Oleg Hoefling]

This is a follow-up of https://bugs.launchpad.net/lxml/+bug/1880251 (fixed in 4.5.2). I'm extracting the comment https://bugs.launchpad.net/lxml/+bug/1880251/comments/3 to a separate issue:

### Version info

Python : sys.version_info(major=3, minor=8, micro=3, releaselevel='final', serial=0)
lxml.etree : (4, 5, 2, 0)
libxml used : (2, 9, 10)
libxml compiled : (2, 9, 10)
libxslt used : (1, 1, 34)
libxslt compiled : (1, 1, 34)

### Summary

The description is the same as in https://bugs.launchpad.net/lxml/+bug/1880251, besides that the LXML import now occurs after the xmlsec1 library load:

```python
import ctypes

xmlsec = ctypes.CDLL('/usr/lib/libxmlsec1.so')
xmlsec.xmlSecInit()

from lxml import etree

etree.parse('doc.xml')
etree.parse('doc.xml')
```

yields

```
Traceback (most recent call last):
  File "reader.py", line 23, in <module>
    etree.parse('doc.xml')
  File "src/lxml/etree.pyx", line 3467, in lxml.etree.parse
  File "src/lxml/parser.pxi", line 1839, in lxml.etree._parseDocument
  File "src/lxml/parser.pxi", line 1865, in lxml.etree._parseDocumentFromURL
  File "src/lxml/parser.pxi", line 1769, in lxml.etree._parseDocFromFile
  File "src/lxml/parser.pxi", line 1163, in lxml.etree._BaseParser._parseDocFromFile
  File "src/lxml/parser.pxi", line 601, in lxml.etree._ParserContext._handleParseResultDoc
  File "src/lxml/parser.pxi", line 711, in lxml.etree._handleParseResult
  File "src/lxml/parser.pxi", line 651, in lxml.etree._raiseParseError
  File "b'doc.xml'", line 0
lxml.etree.XMLSyntaxError
```

[scoder (scoder)]

Closing this as a duplicate of a more general bug.