pbrt --format crash with large strings

[shadeops]

Super minor and is more of a curiosity than something that needs fixing, but just wanted flag it regardless.

pbrt-v4/src/pbrt/util/print.h

Lines 262 to 264 in e573399

	std::stringstream ss;
	ss << v;
	*s += formatOne(nextFmt.c_str(), ss.str().c_str());

On my system,g++ (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0, the above will fail when the input string is longer than 2^31.

terminate called after throwing an instance of 'std::bad_alloc'
  what():  std::bad_alloc
Aborted (core dumped)

I suspect the only time that would be an issue if running a --format on a very large Medium. Also there are other tools that can do a similar operation like GNU's fold, in the event you had to tidy some very long lines.

Example scene, that when decompressed is +2GB.
example.pbrt.gz

pbrt --format example.pbrt.gz > /dev/null