repl: fix some reverse-i-search display issues

Part of #6325.
repl: slightly clearer fix for #6312
Revert "Bump openlibm and openspecfun."

This reverts commit 7c0e2997e340c14a3390a972cb1db02f8dff2748.
Lower overhead of @simd coda.
fix large and empty StepRanges. fixes #6353

I think this works, but I will try to make it faster in a future commit.
fix #6360 (repl enters pasted text even if no newline is present)
Merge branch 'master' of github.com:JuliaLang/julia
fix #6361 (invalid expression aborts help mode)
fix #6354 (new repl doesn't complete built-ins)
fix build breakage due to undefined flipsign
make nextfloat(-5.0e-324) === -0.0 as per IEEE standard. fixes #6342
Merge branch 'master' of github.com:JuliaLang/julia
Merge pull request #6363 from tanmaykm/readcsv

readdlm: handle white space after last column properly
Update openspecfun to master and install it properly

The new openspecfun no longer uses headers from openlibm
sources, but relies on them being installed to $(includedir)
instead (cf. 682fb0a). Also make the install commands more
standard and similar to openlibm's.
Replace .dylib with $(SHLIB_EXT)

For consistency within the file.
Merge pull request #6343 from ArchRobison/adr/simdcoda

Speed up coda generated @simd
replace processor => process in parallel computing docs for clarity.
fixes #6341
Merge branch 'master' of github.com:JuliaLang/julia
Merge pull request #6238 from nalimilan/openspecfun

Update openspecfun and install it properly
BigInt: add convert(Float64, ::BigInt) with TODO to fix rounding.

Unfortunately, the GMP function that does this conversion truncates
inexact values, rather than rounding to the nearest double.