implicit function declarations issue

[chenrui333]

seeing some implicit function declarations issue while regression building 0.8.3 release

fastq-sample.c:162:9: error: call to undeclared library function 'snprintf' with type 'int (char *, unsigned long, const char *, ...)'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
        snprintf(output_name, output_len, "%s.fastq", prefix);
        ^
fastq-sample.c:162:9: note: include the header <stdio.h> or explicitly provide a declaration for 'snprintf'