Implement block-size market based equilibrium.

This removes BIP109, 2MB blocksize proposal.
In its pace I insert the concept of market equilibrium based blocksizing.
Technically this means;

* We remove from the consensus rules the max-block-size.
* We introduce a command-line-argument that defines the max-block-size it
  will accept from other nodes.

Classic chose to use -blocksizeacceptlimit as a descriptive name, but for
compatibility with BU has an alias for its -excessiveblocksize.
Values are in whole megabytes, but floating point values are accepted with
an accuracy up to 100KB.  So, you can have "3.5" as blocksizeacceptlimit.
This value will be put in the coinbase-comment as "EB3.5" in this example.

In short;
Miners can continue to use the -blockmaxsize argument or bitcoin.conf
setting to limit the size of blocks they generate!  All nodes can also use
the `-blocksizeacceptlimit` option to limit the size of the blocks accepted
from (other) miners.

qa/pull-tester/rpc-tests.py

@@ -117,7 +117,6 @@
     'bip65-cltv-p2p.py',
     'bipdersig-p2p.py',
     'bipdersig.py',
-    'bigblocks.py',
     'getblocktemplate_longpoll.py',
     'getblocktemplate_proposals.py',
     'txn_doublespend.py',

qa/rpc-tests/p2p-fullblocktest.py

@@ -25,6 +25,8 @@ def __init__(self, tx = CTransaction(), n = -1):
 each test.
 '''
 
+MAX_BLOCK_SIZE = 1000000
+
 class FullBlockTest(ComparisonTestFramework):
 
     ''' Can either run this test as 1 node with expected answers, or two and compare them. 
@@ -39,6 +41,10 @@ def __init__(self):
         self.tip = None
         self.blocks = {}
 
+    def setup_nodes(self):
+        return start_nodes(4, self.options.tmpdir,
+                extra_args = [["-maxblocksize=1000000", "--blocksizeacceptlimit=1"]])
+
     def run_test(self):
         test = TestManager(self, self.options.tmpdir)
         test.add_all_connections(self.nodes)
@@ -349,7 +355,7 @@ def update_block(block_number, new_transactions):
         tx.vout = [CTxOut(0, script_output)]
         b24 = update_block(24, [tx])
         assert_equal(len(b24.serialize()), MAX_BLOCK_SIZE+1)
-        yield rejected(RejectResult(16, b'bad-blk-length'))
+        yield rejected()
 
         b25 = block(25, spend=out7)
         yield rejected()

qa/rpc-tests/prioritise_transaction.py

@@ -9,7 +9,9 @@
 
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import *
-from test_framework.mininode import COIN, MAX_BLOCK_SIZE
+from test_framework.mininode import COIN
+
+MAX_BLOCK_SIZE = 1000000
 
 class PrioritiseTransactionTest(BitcoinTestFramework):
 
@@ -24,7 +26,7 @@ def setup_network(self):
         self.nodes = []
         self.is_network_split = False
 
-        self.nodes.append(start_node(0, self.options.tmpdir, ["-debug", "-printpriority=1", "-blockmaxsize=750000"]))
+        self.nodes.append(start_node(0, self.options.tmpdir, ["-debug", "-printpriority=1", "-blockmaxsize=750000", "--blocksizeacceptlimit=1"]))
         self.relayfee = self.nodes[0].getnetworkinfo()['relayfee']
 
     def run_test(self):

qa/rpc-tests/test_framework/mininode.py

@@ -37,7 +37,6 @@
 MY_SUBVERSION = b"/python-mininode-tester:0.0.2/"
 
 MAX_INV_SZ = 50000
-MAX_BLOCK_SIZE = 1000000
 
 COIN = 100000000L # 1 btc in satoshis