More OpenBSD cleanup (primarily string).

This patch removes the string/ and wchar/ directories.

Change-Id: Ia489904bc67047e4bc79acb1f3eec21aa3fe5f0d
diff --git a/libc/arch-arm/generic/generic.mk b/libc/arch-arm/generic/generic.mk
index 063d893..2bc84e0 100644
--- a/libc/arch-arm/generic/generic.mk
+++ b/libc/arch-arm/generic/generic.mk
@@ -1,9 +1,9 @@
 libc_bionic_src_files_arm += \
     arch-arm/generic/bionic/memcpy.S \
     arch-arm/generic/bionic/memset.S \
-    string/strcat.c \
     arch-arm/generic/bionic/strcmp.S \
     arch-arm/generic/bionic/strcpy.S \
     arch-arm/generic/bionic/strlen.c \
     bionic/__strcat_chk.cpp \
     bionic/__strcpy_chk.cpp \
+    upstream-openbsd/lib/libc/string/strcat.c \