Move __aeabi* symbols to LIBC_N version

We had these symbols incorrectly versioned as LIBC_PRIVATE
in M release. This change moves __aeabi* symbols from LIBC
to LIBC_N and adds __gnu_Unwind_Find_exidx to the list

Bug: https://github.com/android-ndk/ndk/issues/1
Change-Id: I0b353012adeacb00ae29ea10c63b9d1cf1cadbe7
diff --git a/libc/arch-arm/bionic/__aeabi.c b/libc/arch-arm/bionic/__aeabi.c
index 098c553..1620d45 100644
--- a/libc/arch-arm/bionic/__aeabi.c
+++ b/libc/arch-arm/bionic/__aeabi.c
@@ -165,7 +165,7 @@
 }
 
 #define __AEABI_SYMVERS(fn_name) \
-__asm__(".symver " #fn_name "_impl, " #fn_name "@@LIBC"); \
+__asm__(".symver " #fn_name "_impl, " #fn_name "@@LIBC_N"); \
 __asm__(".symver " #fn_name "_impl2, " #fn_name "@LIBC_PRIVATE")
 
 __AEABI_SYMVERS(__aeabi_atexit);