str/cat: Rename from util/string

This still maintains backwards compatability.

Change-Id: Id984a9c2067aaa6986f892c1870834d77b8aec80
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/src/meson.build b/src/meson.build
index 464bade..2a08ac5 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -50,8 +50,8 @@
   'pinned.cpp',
   'raw.cpp',
   'signal.cpp',
+  'str/cat.cpp',
   'util/cexec.cpp',
-  'util/string.cpp',
   'zstring.cpp',
   'zstring_view.cpp',
 ]