gltfpack: Fix output animation start time

Due to a bug in resampling logic, minimum time value was always 0 - this
could result in animations that were too long, potentially causing
issues for the client side playback.

Note that if there are no tracks, mint stays at FLT_MAX and we correct
it by clamping it to max (so both end up 0) - this shouldn't happen
normally, and animations without tracks shouldn't be output, but it can
happen in rare edge cases and it's better to fix this up early instead
of triggering issues with timing logic later.

Reported in zeux#185.

gltf/animation.cpp

@@ -3,6 +3,7 @@
 
 #include <algorithm>
 
+#include <float.h>
 #include <math.h>
 #include <string.h>
 
@@ -262,7 +263,7 @@ static void getBaseTransform(Attr* result, size_t components, cgltf_animation_pa
 
 void processAnimation(Animation& animation, const Settings& settings)
 {
-	float mint = 0, maxt = 0;
+	float mint = FLT_MAX, maxt = 0;
 
 	for (size_t i = 0; i < animation.tracks.size(); ++i)
 	{
@@ -273,6 +274,8 @@ void processAnimation(Animation& animation, const Settings& settings)
 		maxt = std::max(maxt, track.time.back());
 	}
 
+	mint = std::min(mint, maxt);
+
 	// round the number of frames to nearest but favor the "up" direction
 	// this means that at 10 Hz resampling, we will try to preserve the last frame <10ms
 	// but if the last frame is <2ms we favor just removing this data