[xml] Initial implementation of core:encoding/xml.

A from-scratch XML implementation, loosely modeled on the [spec](https://www.w3.org/TR/2006/REC-xml11-20060816).

Features:
		- Supports enough of the XML 1.0/1.1 spec to handle the 99.9% of XML documents in common current usage.
		- Simple to understand and use. Small.

Caveats:
		- We do NOT support HTML in this package, as that may or may not be valid XML.
		  If it works, great. If it doesn't, that's not considered a bug.

		- We do NOT support UTF-16. If you have a UTF-16 XML file, please convert it to UTF-8 first. Also, our condolences.
		- <[!ELEMENT and <[!ATTLIST are not supported, and will be either ignored or return an error depending on the parser options.

TODO:
- Optional CDATA unboxing.
- Optional `&gt;`, `&#32;`, `&#x20;` and other escape substitution in tag bodies.
- Test suite

MAYBE:
- XML writer?
- Serialize/deserialize Odin types?

tests/core/build.bat

@@ -5,34 +5,35 @@ python3 download_assets.py
 echo ---
 echo Running core:image tests
 echo ---
-%PATH_TO_ODIN% run image    %COMMON%
+%PATH_TO_ODIN% run image    %COMMON% -out:test_image.exe
 
 echo ---
 echo Running core:compress tests
 echo ---
-%PATH_TO_ODIN% run compress %COMMON%
+%PATH_TO_ODIN% run compress %COMMON% -out:test_compress.exe
 
 echo ---
 echo Running core:strings tests
 echo ---
-%PATH_TO_ODIN% run strings %COMMON%
+%PATH_TO_ODIN% run strings %COMMON% -out:test_strings.exe
 
 echo ---
 echo Running core:hash tests
 echo ---
-%PATH_TO_ODIN% run hash %COMMON% -o:size
+%PATH_TO_ODIN% run hash %COMMON% -o:size -out:test_hash.exe
 
 echo ---
 echo Running core:odin tests
 echo ---
-%PATH_TO_ODIN% run odin %COMMON% -o:size
+%PATH_TO_ODIN% run odin %COMMON% -o:size -out:test_odin.exe
 
 echo ---
 echo Running core:crypto hash tests
 echo ---
-%PATH_TO_ODIN% run crypto %COMMON%
+%PATH_TO_ODIN% run crypto %COMMON% -o:speed -out:test_crypto.exe
 
 echo ---
 echo Running core:encoding tests
 echo ---
-%PATH_TO_ODIN% run encoding %COMMON%
+%PATH_TO_ODIN% run encoding\json %COMMON% -out:test_json.exe
+%PATH_TO_ODIN% run encoding\xml %COMMON% -out:test_xml.exe