Bugfix/2632 luaccrash

[ziggurat29]

Fixes #2632 .

• This PR is for the dev branch rather than for master.
• This PR is compliant with the other contributing guidelines as well (if not, please describe why).
• I have thoroughly tested my contribution.
• The code changes are reflected in the documentation at docs/en/*. ??? I see no such path.

A block of memory is accessed after having been freed. This was obscured by the fact that 'oBuf' is a pointer into the middle of the block 'dynamicTables', so when dynamicTables is freed, oBuf is pointing to freed memory. Occasionally, luac.cross would crash because of this.

[TerryE]

Looking at the code, you can see that at about line 224:

 oBuf          = (struct outputBuf *)(dt+1);

so, oBuf is pointing /into/ the dt chunk. Also note, dt is an alias of dynamicTables.

Uuuuaaaargghhh @ziggurat29. Mea cupla; mea culpa.