all: char_buf_array -> CStringN
header: make Append return a pointer to the updated Header
header: add not-impl. panics
file: remove named returns
test: add TestCreateFile
header: add convenience function NewDefaultHeader
c-utils: add long_array_new
image: Write image
phdu: add NewPrimaryHDU
test: add TestCreatePHDU
table: govalue_from_typecode. prelim. support for VLA
table: first stab at NewTable