restructure dump.c slightly to make it more flexible
WIP: progress towards serializing/deserializing a single module at a time
WIP: add support for forward value references in the backref table
WIP: rehash affected method tables due to datatype->uid changes after restoring
be alot more careful about serializing types, especially ones that are also methods, and minor corrections
serialize methlist in reverse order to stabilize method order after deserializing (see #8652 for cause). note this causes more nuisance ambiguity warnings
fix #8698: cp(src,dst) should truncate dst if it already exists
ndigits0z(n::BigInt, b): avoid expensive off-by-one check for b=2^k.

Fixes #8727, but it's kind of a bandaid since for non-power-of-two
bases ndigits0z is still slow due to GMP's inexcusable laziness. At
least for power-of-two bases, however, BigInt hashing is now about
3x faster and allocates no memory.
Merge branch 'master' of github.com:JuliaLang/julia
Merge branch 'jn/static_compile_3'
add some comments for code added under commit "Merge branch 'jn/static_compile_3'"
fix 10x performance regression in stockcorr
Merge pull request #8741 from stevengj/cp_trunc

fix #8698: cp(src,dst) should truncate dst if it already exists
formatting fixes
Merge branch 'master' of https://github.com/JuliaLang/julia into jb/call_constructors

Conflicts:
	src/builtins.c
	src/dump.c
update serializer changes for call_constructors branch