Support for tclreadline

[bfg86]

See issue #59. Basically a copy of what's done in the OpenROAD repository (https://github.com/The-OpenROAD-Project/OpenROAD/issues/136)

[bfg86]

I get this message when opening sta:

application-specific initialization failed: error while autoloading "history": Error: history.tcl, 330 invoked "return" outside of a proc.

Got around it by adding this to my ~/.sta:

if {$tcl_interactive} {
  package require tclreadline
  ::tclreadline::Loop
}

[bfg86]

See @jjcherry56 added tclreadline support in commit 15d9333. Closing