New implementation of root_sourceline

[tomschr]

xmlutil.py:

• Removed VALIDROOTS
• Removed obsolete compilestarttag() function
• Renamed root_sourceline -> findprolog;
• Reimplemented findprolog with xml.sax.handler.ContentHandler and Locator

xmlhandler.py:

• Used corrected function findprolog
• Fixed testcases
• [ ]  General Comment
• <img border=0 src='https://avatars.githubusercontent.com/u/10010231?v=3' height=16 width=16'> Repository health decreased by 1.00% when pulling d9822ab on feature/starttagfix-a into 290ff3e on develop.
• 6 new problems were found (including 1 error and 5 code smells).
• 4 problems were fixed (including 0 errors and 3 code smells).
• <img border=0 src='https://avatars.githubusercontent.com/u/10010231?v=3' height=16 width=16'> Repository health increased by 0.40% when pulling 7fafc98 on feature/starttagfix-a into 290ff3e on develop.
• 1 new problem was found (including 1 error and 0 code smells).
• 4 problems were fixed (including 0 errors and 3 code smells).

  

[landscape-bot]

Repository health decreased by 1.00% when pulling d9822ab on feature/starttagfix-a into 290ff3e on develop.

• 6 new problems were found (including 1 error and 5 code smells).
• 4 problems were fixed (including 0 errors and 3 code smells).

[landscape-bot]

Repository health increased by 0.40% when pulling 7fafc98 on feature/starttagfix-a into 290ff3e on develop.

• 1 new problem was found (including 1 error and 0 code smells).
• 4 problems were fixed (including 0 errors and 3 code smells).