When building this package with clang, an error was reported as following.
This PR fixes the error.

    In file included from sm3.c:15:
    ./sm3.h:17:30: error: redefinition of typedef 'SM3Context' is a C11 feature [-Werror,-Wtypedef-redefinition]
    typedef struct SM3ContextStr SM3Context;
                                 ^
    ./blapit.h:270:30: note: previous definition is here
    typedef struct SM3ContextStr SM3Context;