Allow to disable reference of AES-256-XTS for Themis iOS (#329)

* playing around with boringssl podspec

* minor visual updates for iOS examples, update gitignore

* fix subspec in test podspec

* Update themis.podspec

* podspec name tests

* name tests

* try with boring only

* boringssl podspec: define -DCRYPTO_ENGINE_PATH=BORINGSSL

* -DCRYPTO_ENGINE_PATH=boringssl

* try boringssl-grpc

* move back original boringssl

* workaround and updated boringssl spec for ios

* double spec working

* disable using aes-256-xts in soter for iOS - boringssl

* update ios test to use both openssl and boringssl

* remove SOTER_BORINGSSL_DISABLE_XTS from openssl soter

* fix comments style

src/soter/boringssl/soter_sym.c

@@ -65,8 +65,15 @@ const EVP_CIPHER* algid_to_evp(uint32_t alg){
       return EVP_aes_192_ctr();
     case SOTER_SYM_AES_CTR|SOTER_SYM_128_KEY_LENGTH:
       return EVP_aes_128_ctr();
+/* 
+* Workaround for using BoringSSL on iOS, because XTS is not included in BoringSSL pod implementation.
+* see https://github.com/CocoaPods/Specs/blob/master/Specs/0/8/a/BoringSSL/10.0.6/BoringSSL.podspec.json#L44
+* see https://github.com/cossacklabs/themis/issues/223#issuecomment-432720576
+*/
+#ifndef SOTER_BORINGSSL_DISABLE_XTS
     case SOTER_SYM_AES_XTS|SOTER_SYM_256_KEY_LENGTH:
       return EVP_aes_256_xts();
+#endif
   }
   return NULL;
 }

src/wrappers/themis/Obj-C/objcthemis/objcthemis.h

@@ -7,8 +7,8 @@
 	#import <objcthemis/skeygen.h>
 	#import <objcthemis/smessage.h>
 	#import <objcthemis/scomparator.h>
-    #import <objcthemis/ssession.h>
-    #import <objcthemis/serror.h>
+	#import <objcthemis/ssession.h>
+	#import <objcthemis/serror.h>
 
 #endif /* _OBJCTHEMIS_ */