libsepol: replace non-standard use of __BEGIN_DECLS

While most header files already use the common pattern of `extern "C"`
declarations to enable compiling in a C++ project, some header files in
libsepol instead use the macros `__BEGIN_DECLS` and `__END_DECLS`. These
macros are defined in the "sys/cdefs.h" header file, which provides
some non-standard extensions for glibc.

Convert usage of these declarations with the standard `extern "C"`
pattern. This improves compatibility with other libc implementations,
e.g. musl libc.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
4 files changed