#41 Name prefix of public API

[Xin Wang]

Currently, public API of CLIPS do not have any prefix, which will have high possibility to be conflict with other systems.

Have looked at some other languages, Tcl has Tcl_ prefix[1], and Lua has lua_ or luaL_[2], both of them are widespread embeddable language.

I think we can take the opportunity of V6.4 API overhaul to add some kind of prefix.

[1] https://tcl.tk/man/tcl8.6/TclLib/contents.htm
[2] http://www.lua.org/manual/5.3/