Manually convert to int to fix octal issue

When relying on Supybot's built-in "int" argument conversion type, any
bug numbers pasted from Mantis that are prefixed by zeroes (eg, 000123)
get interpreted as octal numbers, which results in lookups for the
incnorrect issue.  By using Supybot's "text" conversion type, we can
then use python's int() method to force a conversion to decimal,
regardless of how many zeroes the number is prefixed with.