vectorize lexicographical_compare, lexicographical_compare_three_way

[AlexGuteniev]

Some parts are similar to what we have

• There's already memcmp optimization, so the predicate classification can be reused
• The elements classification can be reused from min/max_element optimization
• The wrappers for intrinsics can also be reused from min/max_element optimization

Scope

• 1 byte integers (for strings, IP addresses, binary data, etc., try to beat memcmp)
• 2 byte integers (for wide strings)
• 4 or 8 byte integers (for arrays of integers)
• 4 or 8 byte floats (for arrays of floats, after vectorize min/max_element using SSE4.1 for floats #3928)
• Can support infinite ranges removed in Don't memcmp(x, y, -1) from ranges::lexicographical_compare #3989 again

[CaseyCarter]

• Can support infinite ranges removed in Don't memcmp(x, y, -1) from ranges::lexicographical_compare #3989 again

ranges::lexicographical_compare still supports comparing two infinite ranges, the change is that it won't try to pass them to memcmp.

[AlexGuteniev]

ranges::lexicographical_compare still supports comparing two infinite ranges

Yes, I meant support by optimization, not general support.

[AlexGuteniev]

I struck floats, as on more thought it doesn't seem to make much sense to do lexicographical comparison of array of floats.
I also struck infinite ranges, guess we're not doing that anymore.