Don't create overly large CRAM blocks.

Currently CRAM containers can in some circumstance become huge.  To
prevent this we currently have a limit of the number of sequences
(default 10,000) and also by number of bases (default 500 * number of
seqs) so long-read technologies don't put too much in a container.

However if we have 10k of reads with jointly under 5Mb of sequence
that also have over 2GB worth of aux data, then we can trigger the
overflow fixed in the previous commit.

How do we get >430 bytes worth of aux for every base and >214Kb of aux
for every read, in real world data rather than in deliberate stress
testing?  One possibility is with SEQ "*" (eg secondary alignments
from minimap2) on very long-read data with heavy aux tag usage, as this
doesn't increase base count at all.  The same issue occurs to a lesser
extent which supplementaries and hard-clipping.

We now create new containers when seq+aux goes beyond the specified
limit instead of just seq.  In normal circumstances this will have
a limited effect.

Thanks to Martin Pollard for triggering and reporting this corner case.

cram/cram_encode.c

@@ -3852,7 +3852,7 @@ int cram_put_bam_seq(cram_fd *fd, bam_seq_t *b) {
 
     if (!c->slice || c->curr_rec == c->max_rec ||
         (bam_ref(b) != c->curr_ref && c->curr_ref >= -1) ||
-        (c->s_num_bases >= fd->bases_per_slice)) {
+        (c->s_num_bases + c->s_aux_bytes >= fd->bases_per_slice)) {
         int slice_rec, curr_rec, multi_seq = fd->multi_seq == 1;
         int curr_ref = c->slice ? c->curr_ref : bam_ref(b);
 
@@ -3885,7 +3885,7 @@ int cram_put_bam_seq(cram_fd *fd, bam_seq_t *b) {
 
         if (CRAM_MAJOR_VERS(fd->version) == 1 ||
             c->curr_rec == c->max_rec || fd->multi_seq != 1 || !c->slice ||
-            c->s_num_bases >= fd->bases_per_slice) {
+            c->s_num_bases + c->s_aux_bytes >= fd->bases_per_slice) {
             if (NULL == (c = cram_next_container(fd, b))) {
                 if (fd->ctr) {
                     // prevent cram_close attempting to flush
@@ -3997,6 +3997,7 @@ int cram_put_bam_seq(cram_fd *fd, bam_seq_t *b) {
     c->curr_rec++;
     c->curr_c_rec++;
     c->s_num_bases += bam_seq_len(b);
+    c->s_aux_bytes += bam_get_l_aux(b);
     c->n_mapped += (bam_flag(b) & BAM_FUNMAP) ? 0 : 1;
     fd->record_counter++;
 

cram/cram_structs.h

@@ -473,6 +473,7 @@ struct cram_container {
     uint32_t crc32;       // CRC32
 
     uint64_t s_num_bases; // number of bases in this slice
+    uint64_t s_aux_bytes; // number of bytes of aux in BAM
 
     uint32_t n_mapped;    // Number of mapped reads
     int ref_free;         // whether 'ref' is owned by us and must be freed.