Don't try to use MIPS32 asm macros on MIPS64

The MIPS32 bn_mul asm code causes segfaults on MIPS64 and failing
tests. Until someone has time to fix this up, MIPS64 platforms should
fall back to the C implementation (which works fine).

ChangeLog

@@ -30,6 +30,8 @@ Bugfix
    * Fixed CMake symlinking on out-of-source builds
    * Fixed dependency issues in test suite
    * Programs rsa_sign_pss and rsa_verify_pss were not using PSS since 1.3.0
+   * Bignum's MIPS-32 assembly was used on MIPS-64, causing chaos. (Found by
+     Alex Wilson.)
 
 = PolarSSL 1.3.4 released on 2014-01-27
 Features

include/polarssl/bn_mul.h

@@ -770,7 +770,7 @@
     );
 #endif /* Alpha */
 
-#if defined(__mips__)
+#if defined(__mips__) && !defined(__mips64__)
 
 #define MULADDC_INIT            \
     asm(                        \