Only show completion options on the 2nd tab-press

Instead of the current complete-or-show-possible-completions behavior, this now requires a second consecutive tab press to show the possible completions. This behaves a little bit more like most shells, and prevents excessive printing of options in most cases.
Use repeated keystrokes for move_line_start/end

Jump to the start/end of input upon a repeated keystroke instead of detecting that the cursor is already at the beginning or end of a line. This way the behavior changes based purely upon the input instead of relying on where the cursor happens to be.
fix #7248: throw boundserror for invalid indices in ind2chr/chr2ind
improve fix for #7227: handle dsymutil versions containing .
Suppress "unused variable" warning
added convert(::Type{UUID}, ::String) removed convert(::Vector{Uint8}, ::UUID)
Merge pull request #7237 from shashi/uuid_conversion

added convert(::Type{UUID}, ::ASCIIString)
add checkbounds(s::String, I)
fix typo in #7237
Add tests for kill/yank and move_line_end/start

Fix a discovered inconsistency in the behavior of move_line_start.

Test with repeated inputs.
Add missing -lgfortran flag to a openblas makefile

This allows openblas v0.2.9 to be compiled on Windows.
REPL: Moving left and right was skipping newlines

Issue #7210 fixed movement across combining characters, such that moving left
and right by one character would skip all zero-width characters, but this also
inadvertently includes newlines. This made it impossible to navigate to the end
of a line that ended with a newline with the left and right arrows alone. And movement across multiple newlines would skip across them all at once.

This fixes that and adds simple regression tests.
Merge pull request #7211 from andrioni/add_significand

Add significand to BigFloat, fix #7207
Merge pull request #7220 from tkelman/patch-4

fix #7203 and #7218
Merge pull request #7253 from mbauman/char-move-skips-newlines

REPL: Moving left and right was skipping newlines
Merge pull request #7249 from stevengj/ind2chr_bounds

fix #7248: throw boundserror for invalid indices in ind2chr/chr2ind
isvalid() chr2ind() ind2chr() for SubString of DirectIndexString
Merge pull request #7255 from davidanthoff/fixopenblasbuilderroronwin

Add missing -lgfortran flag to a openblas makefile
fix szfile and szarray values

replace 0xffffffff with typemax(Uint32)
add a test with a larger offset than 64k
use div(a, b) instead of ifloor(a/b)
make 'julia --help' output more uniform in style. Also update manpage, and getting started guide for latest flags.