net/ntp: Fix untracked gettext dependency & lots more

ntp links against gettext (libintl) if it is installed on the system:

• Add an NLS OPTION to explicitly enable, disable and track libintl dependency
• Add DEBUG and THREADS OPTIONS. Keep the latter enabled by OPTIONS_DEFAULT to preserve compatibility with existing behaviour.
• Explicitly pass OpenSSL include / library dir paths to configure
• Unsilence install command
• Enable verbose building (--disable-silent-rules)
• Use TOUCH variable instead of hardcoded command
• Add TEST_TARGET to enable test suite
• Patch sntp tests to ensure they link correctly to threading library
• Pet portlint (*_DEPENDS order, group USE{S} sections, sort OPTIONS)

Approved by: cy (maintainer)
Differential Revision: D4812
MFH: 2016Q1