This prevents the undefined behaviour that would come up as a result of
doing so. (For example: opening "infinite" devices like /dev/full will
result in an infinite loop until exhaustion of memory)
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
This adds a new structure 'Typeface' to the FontDatabase that
represents all fonts of the same family and variant.
It can contain a list of BitmapFonts with varying size but of
the same family and weight or a pointer to a single TTF font
for all sizes of this Typeface.
