libmagic: fix file identification

libmagic: fix file identification

Removes local modifications from contrib code and
fixes at least the following identification issue.

Before:

    # file /usr/src/bin/test/test.c
    /usr/src/bin/test/test.c: ASCII text

After:

    # file /usr/src/bin/test/test.c
    /usr/src/bin/test/test.c: C source, ASCII text