Adds additional zero checks for setCompact
 These encoded values should all decode to zero

   Positive Numbers
    0x01003456 (1 byte  0x00)
    0x02000056 (2 bytes 0x0000)
    0x03000000 (3 bytes 0x000000)
    0x04000000 (4 bytes 0x000000_00)

   Negative Numbers
    0x00923456 -(0 bytes, so zero)
    0x01803456 -(1 byte  0x00)
    0x02800056 -(2 bytes 0x0000)
    0x03800000 -(3 bytes 0x000000)
    0x04800000 -(4 bytes 0x000000_00)
add test of DecodeBase58 skipping whitespace
Merge pull request #3712

a3138ed add test of DecodeBase58 skipping whitespace (Christian von Roques)
Merge pull request #3559

e6c6bc9 Adds additional zero checks for setCompact  These encoded values should all decode to zero (Noel Tiernan)