[PATCH] support tab-completion for single quote input with equal sign

Hi

I found a problem when using tab-completion as follows:

CREATE SUBSCRIPTION my_subscription
CONNECTION 'host=localhost port=5432 dbname=postgres' [TAB]

The word 'PUBLICATION' couldn't be auto completed as expected.

The reason is that the equal sign in a single quote is taken as WORD_BREAKS.
Which causes words count is not correct for a input command string.

Fix the problem in the attached patch. By fix this, "\t\n@$><=;|&{() " will not be taken as WORD_BREAKS in single
quotedinput string. 
Please be kindly to take a look at the fix and kindly to tell me if you find any scenario affected by the fix.

Regards,
Tang