streq(), wcseq(): New functions to compare strings for equality

[Wilco Dijkstra]

Hi Alejandro,

If it were an inline function or macro it seems fine as syntactic sugar.
However I think it would be wrong to define this as an exported symbol
that must be supported by libraries - either you end up with 2 copies of
strcmp (bad) or you end up calling a small streq function which calls
strcmp and adjusts the return value (also bad).

Eg. on AArch64 streq looks like:

streq:
        stp     x29, x30, [sp, -16]!
        mov     x29, sp
        bl      strcmp
        cmp     w0, 0
        ldp     x29, x30, [sp], 16
        cset    w0, eq
        ret

That's a lot of extra overhead, so most people would continue using

#define streq(X,Y) strcmp(X,Y) == 0

as that's simpler and faster.

Inlined it would essentially become a nop - and it would make it possible
to add a new symbol similar to __memcmpeq to enable implementations
that only provide eq/ne return value.

Cheers,
Wilco