Appease clang -Wshadow

The macros BSWAP4 and BSWAP8 have statetemnt expressions
implementations that use local variable names that shadow variables
outside the macro call, generating warnings like this

e_aes_cbc_hmac_sha1.c:263:14: warning: declaration shadows a local variable
      [-Wshadow]
    seqnum = BSWAP8(blocks[0].q[0]);
             ^
../modes/modes_lcl.h:41:29: note: expanded from macro 'BSWAP8'
                            ^
e_aes_cbc_hmac_sha1.c:223:12: note: previous declaration is here
    size_t ret = 0;
           ^

Have clang be quiet by modifying the macro variable names slightly
(suffixing them with an underscore).
Reviewed-by: NRich Salz <rsalz@openssl.org>

crypto/modes/modes_lcl.h

@@ -38,36 +38,36 @@ typedef unsigned char u8;
 #if !defined(PEDANTIC) && !defined(OPENSSL_NO_ASM) && !defined(OPENSSL_NO_INLINE_ASM)
 # if defined(__GNUC__) && __GNUC__>=2
 #  if defined(__x86_64) || defined(__x86_64__)
-#   define BSWAP8(x) ({ u64 ret=(x);                    \
+#   define BSWAP8(x) ({ u64 ret_=(x);                   \
                         asm ("bswapq %0"                \
-                        : "+r"(ret));   ret;            })
-#   define BSWAP4(x) ({ u32 ret=(x);                    \
+                        : "+r"(ret_));   ret_;          })
+#   define BSWAP4(x) ({ u32 ret_=(x);                   \
                         asm ("bswapl %0"                \
-                        : "+r"(ret));   ret;            })
+                        : "+r"(ret_));   ret_;          })
 #  elif (defined(__i386) || defined(__i386__)) && !defined(I386_ONLY)
-#   define BSWAP8(x) ({ u32 lo=(u64)(x)>>32,hi=(x);     \
+#   define BSWAP8(x) ({ u32 lo_=(u64)(x)>>32,hi_=(x);   \
                         asm ("bswapl %0; bswapl %1"     \
-                        : "+r"(hi),"+r"(lo));           \
-                        (u64)hi<<32|lo;                 })
-#   define BSWAP4(x) ({ u32 ret=(x);                    \
+                        : "+r"(hi_),"+r"(lo_));         \
+                        (u64)hi_<<32|lo_;               })
+#   define BSWAP4(x) ({ u32 ret_=(x);                   \
                         asm ("bswapl %0"                \
-                        : "+r"(ret));   ret;            })
+                        : "+r"(ret_));   ret_;          })
 #  elif defined(__aarch64__)
-#   define BSWAP8(x) ({ u64 ret;                        \
+#   define BSWAP8(x) ({ u64 ret_;                       \
                         asm ("rev %0,%1"                \
-                        : "=r"(ret) : "r"(x)); ret;     })
-#   define BSWAP4(x) ({ u32 ret;                        \
+                        : "=r"(ret_) : "r"(x)); ret_;   })
+#   define BSWAP4(x) ({ u32 ret_;                       \
                         asm ("rev %w0,%w1"              \
-                        : "=r"(ret) : "r"(x)); ret;     })
+                        : "=r"(ret_) : "r"(x)); ret_;   })
 #  elif (defined(__arm__) || defined(__arm)) && !defined(STRICT_ALIGNMENT)
-#   define BSWAP8(x) ({ u32 lo=(u64)(x)>>32,hi=(x);     \
+#   define BSWAP8(x) ({ u32 lo_=(u64)(x)>>32,hi_=(x);   \
                         asm ("rev %0,%0; rev %1,%1"     \
-                        : "+r"(hi),"+r"(lo));           \
-                        (u64)hi<<32|lo;                 })
-#   define BSWAP4(x) ({ u32 ret;                        \
+                        : "+r"(hi_),"+r"(lo_));         \
+                        (u64)hi_<<32|lo_;               })
+#   define BSWAP4(x) ({ u32 ret_;                       \
                         asm ("rev %0,%1"                \
-                        : "=r"(ret) : "r"((u32)(x)));   \
-                        ret;                            })
+                        : "=r"(ret_) : "r"((u32)(x)));  \
+                        ret_;                           })
 #  endif
 # elif defined(_MSC_VER)
 #  if _MSC_VER>=1300