reordering warning with g++ in HierarchicalNSW

[jlmelville]

The initializer in the third constructor for HierarchicalNSW has label_op_locks_ and link_list_locks_(max_elements) initialized in a different order to their declaration (on line 42 and 39, respectively):

hnswlib/hnswlib/hnswalg.h

Lines 95 to 96 in 359b2ba

	: link_list_locks_(max_elements),
	label_op_locks_(MAX_LABEL_OPERATION_LOCKS),

This causes a -Wreorder warning to be emitted by g++. Not a big deal admittedly, but I was hoping to finally get the R bindings up to date, and a compiler warning will be grounds for rejection by CRAN (not anyone's problem but mine).

Happy to provide a PR, although the fix is as trivial as swapping the position of the two initializers.

[yurymalkov]

Hi @jlmelville, sorry for the long response.
Yeah, a PR would be welcomed! Thanks!