wire: check TXID length before creating outpoint

[jharveyb]

chainhash.NewHashFromStr will zero-pad the given string if it's smaller than 32 bytes / 64 hex chars.

That's fine, but when creating an OutPoint from a string, the TXID part of the string must be exactly 64 hex chars to (possibly) be a valid TXID. Right now, NewOutPointFromString accepts a TXID of less than 64 chars, and will end up padding the end with 0's.

This PR rejects incorrectly-sized TXID strings in NewOutPointFromString.

[coveralls]

Pull Request Test Coverage Report for Build 10394619593

Details

• 3 of 3 (100.0%) changed or added relevant lines in 1 file are covered.
• 6 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.006%) to 57.232%

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Files with Coverage Reduction	New Missed Lines	%
peer/peer.go	6	74.16%

Totals
Change from base Build 10312227216:	-0.006%
Covered Lines:	29841
Relevant Lines:	52140

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💛 - Coveralls

[Roasbeef]

LGTM 💿