Efficient string concatenation

[Caolán McNamara]

On Sun, 2012-12-02 at 22:59 -0600, Norbert Thiebaud wrote:
> vaguely related... since we are talking about performance... why
> *_new_WithLength() in strtmpl.cxx is doing a memset on the whole newly
> allocated buffer...

yeah, someone noticed that when writing i18npool/i18nutil and wrote a
non-memsetting version which I moved into comphelper as
rtl_uString_alloc/rtl_string_alloc

c.