REPL: fix incomplete input detection in return_callback

Hopefully addresses part of #6420
REPL: ^K should only kill up to a newline

Addresses part of #6420
do build and install julia/Rmath-julia.so
a few minor spelling & whitespace tweaks
Merge pull request #6093 from alyst/master

do build and install julia/Rmath-julia.so
Fix #6424 (tab completion of macros)
fix #6404
check length() of Int64 ranges on 32-bit. hopefully fixes #6396
fix #6431 (more reverse-i-search problems)
Integrate gsl-shell/luajit into microbenchmarks

- Also update command to get Julia version info.
- Renames label for gsl-shell/lua tests from gsl_shell to lua.
- Remove non-working external BLAS usage warning

Closes #1662.
Merge pull request #6430 from JuliaLang/cjh/fix-1662

Integrate gsl-shell/luajit into microbenchmarks
fix #6415