Fix for failed build on Linux "Invalid_argument"

[BigBallWiggles]

I went to install BitcoinZ in Linux and I got an error when compiling saying 'Invalid_argument' undefined or something. I also noticed the 'curl' dependency on the directions wasn't listed which was an easy one, but I Googled about the 'Invalid_argument' and someone on Stack Overflow said "it is defined in the header stdexcept Include it..." So I went into crypto/equihash.h and added " #include stdexcept.h " and saved it and it built successfully.

I actually used the greater than and less than signs without the .h Github seemed not to like the greater than and less than signs

[MarcelusCH]

I guess @ezzygarmyz patches could solve this. We should check about to merge this (and others deps PR) into a new branch, and find testers to validate a rc version.