fix: use angle brackets for includes under include/mitie

[peter277]

Makes include style and resolution behaviour consistent across include/mitie. Angle brackets are already the main convention.

[davisking]

Why though? Is this fixing something? This has the possibility to break certain user's build systems.

[peter277]

Why though? Is this fixing something? This has the possibility to break certain user's build systems.

The motivation is include resolution safety and consistency. I'm using MITIE in an MSYS2 package alongside an external dlib, and mixing quoted includes and angle brackets creates a risk of mis-resolution if a nearby directory contains similarly named headers. I would rather avoid patching this downstream, hence submitting the PR.

Angle brackets are also already the prevailing convention in include/mitie (for example:

MITIE/mitielib/include/mitie/approximate_substring_set.h

Lines 8 to 9 in 6299375

	#include <dlib/uintn.h>
	#include <dlib/serialize.h>

and

MITIE/mitielib/include/mitie/binary_relation_detector.h

Lines 7 to 11 in 6299375

	#include <dlib/hash.h>
	#include <dlib/svm.h>
	#include <dlib/serialize.h>
	#include <vector>
	#include <mitie/total_word_feature_extractor.h>

among many others), so this change just aligns the remaining headers.

Could you outline a concrete scenario in which switching these to angle brackets would break a build? From my perspective, this is low risk and may actually prevent subtle issues.