Shift two issue numbers in strings like issue([0-9]+), see faedd55

I'm not sure about the #4021 (old issue number 922), maybe
it's #4087.  This issue number looks as a typo for me (998 instead
of 988 in the old bugtracker).  Test was added in the #4021 (commit
a945bc6), but it works only with modifications from #4087 (issue
988, commit 3741e80).

[skip ci]
Merge pull request #7583 from skirpichev/shift-issue-numbers3

Shift two issue numbers (see #7579)
Fixed bug in ``_minpoly_op_algebraic_element``, see issue 7574
Added test for issue 7574
Added arg tests, modified simplify and trigsimp code
Merge branch 'master' of https://github.com/sympy/sympy into basicvector