ptpd2: fix build failures due to EVP_MD_CTX conflict and U64 missing

ptpd2: fix build failures due to EVP_MD_CTX conflict and U64 missing

In src/dep/ntpengine/ntp_isc_md5.*, the typedef of EVP_MD_CTX
conflicts with a definition of the same type done by OpenSSL. This
issue is referenced at https://github.com/ptpd/ptpd/issues/54, and has
been fixed upstream in commit
https://github.com/ptpd/ptpd/commit/838b985510c360e651d18134e64f258f2f4c6e7c.

In src/dep/snmp.c, U64 can be missing or conflicts with new perl as
reported at https://github.com/ptpd/ptpd/issues/25. This issue has
been fixed upstream in commit
https://github.com/ptpd/ptpd/commit/1886522b50fe44e5c0dedd01d13ac456b941f744. This
commit is adapted to apply on the current version of ptpd2 we have in
Buildroot.

Fixes:
http://autobuild.buildroot.net/results/47b99a6de256bfc0f5a8ae1484bb34e93b407237/
http://autobuild.buildroot.net/results/08365fc559dda74640b9750358c82e84600a68ea/
http://autobuild.buildroot.net/results/9b41c513500c63a9890973a0f17ffdb84d44d580/
http://autobuild.buildroot.net/results/2ed79d01635c9a5e1018229dc6f4b7240a995b87/
http://autobuild.buildroot.net/results/6d1b7e191f573334115684b85165f2bc27d75d8f/
http://autobuild.buildroot.net/results/f54c6fd841b3ea77dc12048c81f3f2991b679252/
http://autobuild.buildroot.net/results/332bc77bcde0bef1b2fd7b9993409dd051c27cd6/
http://autobuild.buildroot.net/results/4b416edaec9528d75a82c9570b8f8297718ca62d/

Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>