This would be a great job for a Perl one-liner with paragraph mode enabled. If there were a blank line between all the function definitions and the prototypes, you could use a simple:

perl -n00e 'print if /^\d/;' filename

However, since the second prototype doesn't have a blank line, you need to take that into account, with something like:

perl -n00e '/^(\d(.(?!\nPrototype))+)/ms; print $1' filename

This will search for any paragraph that starts with a number, then look for as many characters as it can find that aren't followed by \nPrototype.

If the file doesn't have a blank line before each function definition (except the first), then this won't work, though.

I noticed your code references an HTML file. Are we looking at the raw file here, or the cut-n-paste from a browser? If the raw file is laid out with HTML tags, that will complicate things, and these solutions may not work.