#499 (ok 4.1) On user creation, warn if the user already exists

[Olivier Mueller]

If you create an user with the username of an already
exsiting account, but with a different 'host' setup,
PMA will create the user 'bravely', which is correct.
But this may sometimes be an unwanted thing: a red
warning should be displayed: "Warning: another account
with the same username already existed, maybe you'd
like to check that"

Reason: 2 accounts with the same username but different
passwords can cause problems... :)

[Michal Čihař]

Logged In: YES
user_id=192186

I guess ne0x made none progress on this.

[Marc Delisle]

Logged In: YES
user_id=210714
Originator: NO

This is not yet implemented.

[Sameera Kannangara]

Seems like this feature is related to the feature at [1]
Same problem 'what about user with same "user_name" from different "host"s?' occur in both features.
May be using "User & Host" to identify a user would solve this problem.
WDYT?

[1] https://sourceforge.net/p/phpmyadmin/feature-requests/785/

[Sameera Kannangara]