While there may be better solutions, I needed a varargs function for
building Vulkan specialization data. Like progs functions, negative
parameter counts indicate ellipsis with the number of fixed parameters
being equal to -param_count - 1.
Setting the result type cexpr_exprval tells cexpr to simply return whoe
exprval object rather than the referenced value, thus allowing the
caller to check the type when the expression is context sensitive.
This allows plist objects to be accessed directly from cexpr expressions
using struct.field syntax for dictionary objects and array[index] syntax
for array objects.
The problem is that I needed to support dynamic types on operators (for
bit-field enums), had things working, but a bad edit messed things up
and I had to rebuild that bit of code. Missed one bit :P
It is capable of parsing single expressions with fairly simple
operations. It current supports ints, enums, cvars and (external) data
structs. It is also thread-safe (in theory, needs proper testing) and
the memory it uses can be mass-freed.
