[performance] Do not use block-alloc for pike_frame and catch_context They are too important for code execution speed. struct pike_frames are allocated in chunks but not free:d until the program exists. This is basically just like the normal stack, and for all but the most extreme of recursive programs this is not really an issue. And for those programs the only loss now is that we are not returning the frame memory to the system, we are actually using less memory at peak. The catch_context structures (that are fairly large, anyway, 80 bytes on my machine) are simply allocated using malloc, and up to 100 free ones are kept in a list for quick use.