test: Remove all uses of `~str` from the test suite.
libworkcache: Remove all uses of `~str` from `libworkcache`.
libuuid: Remove all uses of `~str` from `libuuid`.
libhexfloat: Remove all uses of `~str` from `libhexfloat`
libarena: Remove all uses of `~str` from `libarena`
libregex: Remove all uses of `~str` from `libregex`
libgraphviz: Remove all uses of `~str` from `libgraphviz`.
liblog: Remove all uses of `~str` from `liblog`
libglob: Remove all uses of `~str` from `libglob`
libsemver: Remove all uses of `~str` from `libsemver`
libtime: Remove all uses of `~str` from `libtime`
auto merge of #14170 : pcwalton/rust/detildestr-misclibs, r=alexcrichton

r? @brson