qt: keep a list of requested payments

Keep a list of requested payments in the Receive tab so that a user can
recall previously created requests after closing their windows.

Currently this list is not stored between bitcoin-qt sessions. This can
be implemented later, but it is not clear where it should be stored as
I don't think it belongs in the wallet (maybe in QSettings?)
Move types.h include before ifaddres.h for u_int declaration
[Qt] allow deletion of payment-requests in sendcoins

- this adds a delete button for insecure and secure payment requests in
  the sendcoins dialog
- it also enables the delete button even for single and empty entries, as
  this is much easier to handle and doesn't need to special case single
  entries
- big parts of the ui file were changed, because I copied the delete
  button and had to delete the layout too and created it from scratch
  (which seems to cleanup the rows and colums in the layout also, which is
  nice IMHO)
Integration tests via RPC calls

qa/rpc-tests/wallet.sh runs a three-node -regtest network,
generates a fresh blockchain, and then exercises basic wallet
sending/receiving functionality using command-line RPC.
prevent Windows redefinition warning cause by compat.h
autogen.sh: Add a /bin/sh shebang.
autogen.sh: Use set -e to fail if any command fails

In preparation for expanding autogen.sh.
autogen.sh: Support running from outside the source directory

Initial steps towards supporting out-of-tree builds.
autogen.sh: Use long options to autoreconf, for self-documentation
autogen.sh: Stop passing --verbose to autoreconf

This quiets down the autotools build, making warnings much more visible.
configure.ac: Check for miniupnpc headers, not just -lminiupnpc

This protects against broken systems which have libminiupnpc.a or
libminiupnpc.so installed but don't have the miniupnpc headers.
src/Makefile.am: Simplify clean of leveldb
Merge pull request #3321

0078841 prevent Windows redefinition warning cause by compat.h (Philip Kaufmann)
bitcoin-cli: Add missing SelectParamsFromCommandLine

The SelectParamsFromCommandLine call was missing in bitcoin-cli,
which caused `-testnet` and `-regtest` to be ignored. Add this
call just like in bitcoind.cpp.
Merge pull request #3295

9e7776b Integration tests via RPC calls (Gavin Andresen)
Merge pull request #3328

9d2b73d bitcoin-cli: Add missing SelectParamsFromCommandLine (Wladimir J. van der Laan)
mutex debugging routines: LocksHeld() and AssertLockHeld()
Merge pull request #3309

9ac5a01 Move types.h include before ifaddres.h for u_int declaration (Robert Backhaus)
Increase default -blockmaxsize/prioritysize to 750K/50K
Remove dead transaction replacement code

This dead code can be resurrected from git history if
transaction replacement is ever implemented. Keeping
dead code in the source is a bad idea, because it implies
it was tested and worked at some point, which is not true.