Add sane limits for buffers

[prajnoha]

The buffer.h interface allows defining a limit for buffer use:

sid/src/include/base/buffer-common.h

Line 59 in 0fecd48

size_t limit;

sid/src/include/base/buffer.h

Line 38 in 0fecd48

struct buffer *buffer_create(struct buffer_spec *spec, struct buffer_init *init, int *ret_code);

sid/src/include/base/buffer.h

Line 41 in 0fecd48

int buffer_reset_init(struct buffer *buf, struct buffer_init *init);

Audit all the existing code where buffers are used and set a sane limit everywhere so the buffers can't go unlimited if something goes wrong.