float init 0 request

[ABrightLight]

Hello. I understand this subject's been discussed a number of 
times before, but I'd like to throw in my reasoning for why it 
would benefit us more for floats to initialize to 0 than NaN.

1. float is generally used for numeric computation (things like 
NaN boxing are examples of uses outside of this) and as such have 
similarity to the integer types (they will even implicitly coerce 
mathematical operations to float). Since integers default to 0, 
floats should too.

1a. It may be argued that integers only default to 0 because 
there is no meaningful "null" value, but in my opinion this is 
not convincing because I think that most people would opt for 
them getting a reasonable default value right from the start 
instead of being forced to `= 0;` It is very common to see loop 
variables and other forms just say `int i;` or similar, and no 
one is confused by this.

2. It is argued that since, like pointers that have `null` and 
are default initialized to this, floats should also initialize to 
its version of `null`. However this is a false equivalence since 
the use of a null pointer is specified/standardized to crash the 
program due to a concern for memory safety (it's not even set to 
undefined behavior, a program halt must occur). The same memory 
safety concern is not present for most operations relying on 
floats, and the existence of NaN being left without a crash [or 
even an exception thrown] is to cater to performance. For cases 
where debugging by program halt is required, most of the time the 
approach done is for a compiler switch to allow throwing an 
exception instead of just halting the program, since a stack 
trace is presumed to be desired.

3. I know that rikki's DFA implementation will be able to detect 
when a `float x;` occurs without then being actually initialized 
to something useful (keep up the great work rikki!), but this 
particular feature is a special case that is not exactly within 
scope. And the fact that this is even being added as a special 
case should be a hint that leaving NaN as the default init is 
much less useful than some integer-compatible value like 0.

P.S. This subject is a bit subjective (no pun intended) but 
overall we'd likely see more user satisfaction from the float 
init switch. And from what I could tell, it's been well received 
by the OpenD folks, so there's already been a bit of a testbed 
for this.