[Qt] move SubstituteFonts() above ToolTipToRichTextFilter

- doesn't belong to the ToolTipToRichTextFilter class so move it up
Don't poll showmyip.com, it doesn't exist anymore

Fixes #4679.

This leaves us with only one candidate, checkip.dyndns.org.
GetMyExternalIP should be phased out as soon as possible.
Merge pull request #4682

c33b983 Don't poll showmyip.com, it doesn't exist anymore (Wladimir J. van der Laan)
Reapply: Reject transactions with excessive numbers of sigops

Reverting was based on a misunderstanding, it appears.

Github-Pull: #4150
bitcoin-tx: fix build warnings

Cleans up a bunch of:
warning: missing braces around initializer for ‘const<anonymous struct>’
Merge pull request #4696

616c243 bitcoin-tx: fix build warnings (Cory Fields)
Merge pull request #4659

c4bae53 [Qt] move SubstituteFonts() above ToolTipToRichTextFilter (Philip Kaufmann)
build: fix automake warnings about the use of INCLUDES

While we're at it, reduce the use of LIBS as well. This makes dependencies
explicit.

Fixes building with (the not-yet-merged) libsecp256k1 as well.
build: remove some more unused includes vars