new public symbols in 8.3 rc2

[Matthias Klose]

compared to 8.3 rc1, rc2 comes with three new exported symbols, somehow 
cluttering the namespace. seen with a x86_64-linux-gnu build on Debian.

 libreadline.so.8 #PACKAGE# #MINVER#
+ BC@Base 8.3~rc2-1
+ PC@Base 8.3~rc2-1
+ UP@Base 8.3~rc2-1
tcap.h declares these as extern, while terminal.c ends up defining them 
globally.

thanks, Matthias