Avoid unnecessary strlen + memcmp call

[jserv]

Using strncmp() instead of strlen() combined with memcmp() not only reduces the overhead of multiple function calls but also takes advantage of compiler optimizations, such as implicit function inlining.

[fuhsnn]

I was considering

__attribute__((always_inline))
static inline bool equal(Token *tok, char *op) {
  return strlen(op) == tok->len && !memcmp(tok->loc, op, tok->len);
}

or

#define equal(tok, op) (strlen(op) == (tok)->len && !memcmp((tok)->loc, op, (tok)->len))

Since most equal() calls are with compile time string literals, most strlen() are lowered to constants to compilers and the memcmp() can be further transformed to multi-bytes comparisons.

To illustrate:
https://godbolt.org/z/YjMK7az19