docs: Fix a few typos

[timgates42]

There are small typos in:

• docs/behaviors.rst
• src/_pylibmcmodule.c

Fixes:

• Should read while rather than wiile.
• Should read allotted rather than alloted.

Semi-automated pull request generated by https://github.com/timgates42/meticulous/blob/master/docs/NOTE.md

[lericson]

Nice spots, thanks.