regtest: rename memcheck wcpncpy

regtest: rename memcheck wcpncpy

The perl script filter_memcheck removes callstack elements that
are not of interest and changes vg_replace_strmem.c/vg_replace_malloc.c
line numbers to '...'. It protects lines containing the testcase
name.

When the testcase name is the same as the C function being tested
that's not really what we want. My perl isn't really good enough
to be able to only change the line numbers when it is a 'tool file'.
Instead I'm renaming the testcase.