rustc: Add lint for snake_case functions & methods.
libsyntax: Fix snake_case errors.

A number of functions/methods have been moved or renamed to align
better with rust standard conventions.

syntax::ext::mtwt::xorPush => xor_push
syntax::parse::parser::Parser => Parser::new

[breaking-change]
lib{std,core,debug,rustuv,collections,native,regex}: Fix snake_case errors.

A number of functions/methods have been moved or renamed to align
better with rust standard conventions.

std::reflect::MovePtrAdaptor => MovePtrAdaptor::new
debug::reflect::MovePtrAdaptor => MovePtrAdaptor::new
std::repr::ReprVisitor => ReprVisitor::new
debug::repr::ReprVisitor => ReprVisitor::new
rustuv::homing::HomingIO.go_to_IO_home => go_to_io_home

[breaking-change]
lib{serialize, uuid}: Fix snake case errors.

A number of functions/methods have been moved or renamed to align
better with rust standard conventions.

serialize::ebml::reader::Doc => seriaize::ebml::Doc::new
serialize::ebml::reader::Decoder => Decoder::new
serialize::ebml::writer::Encoder => Encoder::new

[breaking-change]
librustc: Fix snake case errors.

A number of functions/methods have been moved or renamed to align
better with rust standard conventions.

rustc::back::link::WriteOutputFile => write_output_file
rustc::middle::ty::EmptyBuiltinBounds => empty_builtin_bounds
rustc::middle::ty::AllBuiltinBounds => all_builtin_bounds
rustc::middle::liveness::IrMaps => IrMaps::new
rustc::middle::liveness::Liveness => Liveness::new
rustc::middle::resolve::NameBindings => NameBindings::new
rustc::middle::resolve::PrimitiveTypeTable => PrimitiveTypeTable::new
rustc::middle::resolve::Resolver => Resolver::new
rustc::middle::trans::datum::Datum => Datum::new
rustc::middle::trans::datum::DatumBlock => DatumBlock::new
rustc::middle::trans::datum::Rvalue => Rvalue::new
rustc::middle::typeck::infer::new_ValsAndBindings => ::infer::unify::ValsAndBindings::new
rustc::middle::typeck::infer::region_inference::RegionVarBindings => RegionVarBindings::new

[breaking-change]
auto merge of #14520 : Ryman/rust/SnakeCaseLint, r=alexcrichton

This enforces `snake_case` for functions and methods only. Might be worth extending it to fields and locals too at some point in the future.

A number of breaking changes each detailed in the attached commits.