Fix POP3 mailcheck aborting because of internal memory errors.

We were using memcpy() with overlapping memory regions, which does not
work. Now, use memmove().

Thanks to Sven-Ola Tuecke <sven-ola at gmx dot de> for finding and
fixing this problem!

BUG: 230072

svn path=/branches/KDE/4.5/kdepimlibs/; revision=1156867