math: fix exp10 not to raise invalid exception on NaN

This was not caught earlier because gcc incorrectly generates quiet
relational operators that never raise exceptions.
fix linked list corruption in flockfile lists

commit 5345c9b884e7c4e73eb2c8bb83b8d0df20f95afb added a linked list to
track the FILE streams currently locked (via flockfile) by a thread.
due to a failure to fully link newly added members, removal from the
list could leave behind references which could later result in writes
to already-freed memory and possibly other memory corruption.

implicit stdio locking was unaffected; the list is only used in
conjunction with explicit flockfile locking.

this bug was not present in any releases; it was introduced and fixed
during the same release cycle.

patch by Timo Teräs, who discovered and tracked down the bug.