fix warnings reported by Coverity

fix warnings reported by Coverity

regcomp.c:126 fixed_size_dest: You might overrun the 100 byte fixed-size string buf by copying s without checking the length
regerror.c:11 fixed_size_dest: You might overrun the 132 byte fixed-size string buf by copying s without checking the length
regexec:174 leaked_storage: Variable relist0 going out of scope leaks the storage it points to