pgsql: Add support for parsing of large XML data (>= 10MB)

Add support for parsing of large XML data (>= 10MB)

This commit adds XML_PARSE_HUGE to the libxml2 functions used in core
for the parsing of XML objects, raising up the original limit of 10MB
supported by libxml2.

In most code paths of upstream, XML_MAX_TEXT_LENGTH (10^7) is the
historical limit that gets upgraded to XML_MAX_HUGE_LENGTH (10^9) once
XML_PARSE_HUGE is given to the parser calls. These are still limited by
any palloc() calls for text, up to 1GB.

This offers the possibility to handle within the backend XML objects
larger than 10MB in general, with also a higher depth limit. This
change affects the contrib module xml2, the xml data type and SQL/XML.

Author: Dmitry Koval
Reviewed-by: Tom Lane, Michael Paquier
Discussion: https://postgr.es/m/18274-98d16bc03520665f@postgresql.org

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/2197d06224a14dba544e05e3df1efcca83bdd9ef

Modified Files
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contrib/xml2/xpath.c | 4 ++--
contrib/xml2/xslt_proc.c | 4 ++--
src/backend/utils/adt/xml.c | 38 +++++++++++++++++++++++++++++---------
3 files changed, 33 insertions(+), 13 deletions(-)