Handle broken rules in the flex_input.l file

[zl90]

• [x] "asdfasd asdf asd" strings are broken (gets parsed as a series of IDs. Note we may need to switch into a different rule set for this, because we are actively ignoring spaces currently, which will break string literals easily).
• [x] Any single character SYMBOL does not get lexed.
• [x] Single character INTEGERs do not get lexed.
• [x] Single character IDs do not get lexed.
• [x] String literals are not being lexed.
• [ ] col_num is not incrementing properly.

[zl90]

There were three problems with my lex input file:

1. I wasn't properly escaping the " quotation marks. They need to be escaped in the file like so: \".
2. I had a general rule for matching "any character": . which simply increments the col_num counter. This rule needs to be defined AFTER all my other rules, or else it seems to override the actions of my other rules.
3. I wasn't incrementing col_num properly. To do that, I needed to access the flex variable yyleng which represents the length of the matched string. It's used like so: col_num += yyleng;.