Update dns.shl

Several changes:

• Added DKIM and DMARC pseudo record types again.
• Added IP support (although it only gives the reverse DNS).
• Made domain an argument and everything else optional flags.

Minor fixes:

• Corrected a variable check which caused the GLUE records to not show when they were actually found.
• Corrected the URL for __core_test() to use the master branch.
• Removed the flag -w for __triton_printerr().