explicit casts for MSVC

extern C on jl_sysimage_name

increase stack size when linking
attempt to get setjmp and longjmp assembly working in MSVC

add .586 to assembly files for masm
MSVC: disable shared libuv library,

extern C on timefuncs, disable sys.dll
use alloca instead of VLA
add getopt.{c,h} from musl-libc for MSVC use

link to license of musl-libc
change .do extension to .dbg.obj

so the compile MSVC wrapper script can recognize the extension
use msvcr120.dll instead of msvcrt.dll for MSVC build

prevent untested MSVC versions from compiling
commit msys_build.sh for reusing dependencies from nightlies
add -DMOJIBAKE_EXPORTS flag when building libmojibake

and when linking flisp
bump mojibake submodule for dllexport fix
replace hex floats with equivalent decimal values
make `a=>b` syntax for `Pair(a,b)`

use Dict(iter) or Dict(::Pair...) as Dict constructors

ref #6739
combine Base.Pair and Base.Collections.Pair

add comparisons for Pair

start fixing tests
fix a mistake I made in priorityqueue in the last commit

add isless for Pair
Merge branch 'master' of github.com:JuliaLang/julia into jb/dictsyntax
Merge branch 'master' of github.com:JuliaLang/julia into jb/dictsyntax
allow parsing => as an identifier, and make it an alias for Pair

this way `a=>b` is lowered like every other operator call, except in
the old dict syntax during the deprecation period.

this is probably a good way to deal with it, and we can later decide to
remove the `Pair` alias if we want to.
update Dict show() to use the new standard syntax
make it trivial for everyone to build the helpdb.jl file
improve documentation for takebuf behavior (#8575)