Presumably these stubs indicate to packagers that external leveldb is meant to
be supported in some way. It is not. Remove the stubs to avoid sending any
mixed messages.
Enable -Wconditional-uninitialized to warn on potentially uninitialized
reads.
Fix the sole such warning in Bitcoin Core in GetRdRand(): r1 would be
set to 0 on rdrand failure, so initializing it to 0 is a non-functional
change.
From "Intel 64 and IA-32 ArchitecturesSoftware Developer's Manual" [1],
page 1711: "CF=1 indicates that the data in the destination is valid.
Otherwise CF=0 and the data in the destination operand will be returned
as zeros for the specified width."
[1] https://software.intel.com/sites/default/files/managed/39/c5/325462-sdm-vol-1-2abcd-3abcd.pdf
leveldb's buildsystem causes us a few problems:
- breaks out-of-tree builds
- forces flags used for some tools
- limits cross builds
Rather than continuing to add wrappers around it, simply integrate it into our
build.
