Update magic.m4 for pkg-config support.
Pkg-config support was added in file 5.39 to fix static linking with libmagic. This patch adds a pkg-config check, which if it fails, defaults back to the old AC_CHECK_LIB.
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Pkg-config support was added in file 5.39 to fix static linking with libmagic. This patch adds a pkg-config check, which if it fails, defaults back to the old AC_CHECK_LIB.