Buffer overflow error in synced_bcf_reader.c

clearly, out is being accessed at location nout, so it should be at least size nout+1.
Merge pull request #142 from reinders/patch-1

Buffer overflow error in synced_bcf_reader.c
Fix compilation when ALLOW_UAC is not defined
bcf_sr_add_reader(): do not increment nreaders or perform any reallocs upon file open errors

This avoids a segfault if bcf_sr_destroy() is called after bcf_sr_add_reader()
when a file couldn't be opened.
Merge pull request #144 from broadinstitute/broad_bcf_sr_add_reader_segfault_fix

bcf_sr_add_reader(): do not increment nreaders or perform any reallocs upon file open errors
bcf_sr_get_header() macro for accessing the synced readers' headers
Add IDX to hdr tags of different type, fixes issue https://github.com/samtools/bcftools/issues/141
1. Modified vcf_parse to update rlen only when an END INFO tag is seen -
the END tag is NOT encoded into v->shared.s
2. Modified vcf_write to add END INFO tag if required:
Add END iff rlen != strlen(reference)
FIXME: what happens when rlen == strlen(reference)? Conditions for
adding END are unclear