Implement <iconv.h>.

Bug: http://b/32978596
Test: ran tests
Change-Id: I56b6ae3d9c5a3a56d2b4afba33fb8f9e964bf7b9
diff --git a/libc/Android.bp b/libc/Android.bp
index be45f40..204ad19 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -1448,6 +1448,7 @@
         "bionic/getpriority.cpp",
         "bionic/gettid.cpp",
         "bionic/grp_pwd.cpp",
+        "bionic/iconv.cpp",
         "bionic/icu_wrappers.cpp",
         "bionic/ifaddrs.cpp",
         "bionic/inotify_init.cpp",