Make the include guards consistent by renaming them systematically according
to the naming conventions below

The public header files (in the 'include/openssl' directory) are not changed
in 1.1.1, because it is a stable release.

For the private header files files, the guard names try to match the path
specified in the include directives, with all letters converted to upper case
and '/' and '.' replaced by '_'. An extra 'OSSL_' is added as prefix.
Reviewed-by: NRichard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9681)

Reviewed-by: NRichard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8347)

If this fails try out if mfspr268 works.

Use OPENSSL_ppccap=0x20 for enabling mftb,
OPENSSL_ppccap=0x40 for enabling mfspr268,
and OPENSSL_ppccap=0 for enabling neither.

Fixes #8012
Reviewed-by: NPaul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/8043)

(cherry picked from commit c8f370485c43729db44b680e41e875ddd7f3108c)

Reviewed-by: NMatt Caswell <matt@openssl.org>

Reviewed-by: NRichard Levitte <levitte@openssl.org>

Reviewed-by: NRichard Levitte <levitte@openssl.org>

Reviewed-by: NKurt Roeckx <kurt@openssl.org>

Reviewed-by: NTim Hudson <tjh@openssl.org>

[and split ppccap.c to ppccap.c and ppc_arch.h]
Reviewed-by: NKurt Roeckx <kurt@openssl.org>
Reviewed-by: NTim Hudson <tjh@openssl.org>