bug#34301: Unable to make underscore part of a word everywhere

[Konstantin Kharlamov <hi-angel@yandex.ru>]

By default the underscore "_" symbol is not being counted as part of a 
word, even though I have never met a language where it's a separate 
entity. This means e.g. that upon opening a file one is never being able 
to "search for word_wth_underscores under cursor", unless they modify 
current table. This problem haunts many people, e.g. this question has 
5576 views for 3 years 11 months 
https://emacs.stackexchange.com/questions/9583/how-to-treat-underscore-as-part-of-the-word

Known workarounds:
	1. Modify syntax table for every mode you happened to stumble upon.
	2. Use superword-mode

Why workarounds are bad:

	1. To make it work one has to search for syntax table name of the 
current mode, and then to modify config file accordingly, every time a 
new mode is being met. That's a lot of actions and research overall, a 
bloating config file; and also lots of work duplication by many Emacs users.
	2. superword-mode doesn't do anything to syntax table, and in 
particular doesn't work with evil-mode.

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It would be great if Emacs has added a function or what not to just keep 
underscore as part of a word for all syntax tables by default.