Code tidyups, fixing various warnings.

Code tidyups, fixing various warnings.

Partial cherry pick of:

Compile with extra warnings turned on. And more makefile/code tidying up.

This turns on most gcc warnings, and removes some unused variables and other code that triggers warnings.
Exceptions are:
 -Wno-sign-compare : triggered by lots of comparisons of signed integer to foo.size(), which is unsigned.
 -Wno-char-subscripts : triggered by the convert-to-hex functions (I may fix this in a future commit).

Conflicts:

	src/makefile.osx
	src/makefile.unix
	src/netbase.cpp
	src/rpc.cpp