[Toybox] why isn't bc_lib a string?

[enh]

the current bc_lib[] seems like an oddly unreadable/undebuggable way to write

scale=20
define e(x){
auto b,s,n,r,d,i,p,f,v
b=ibase
ibase=A
if(x<0){
n=1
x=-x
}
s=scale
r=6+s+.44*x
...