Eliminate unnecessary hash computations in the packrat backend (roughly 2.5x speed in one benchmark)

Hammer gprof

See merge request hammer/hammer!21

Support --gprof build flag

See merge request hammer/hammer!20

h_drop_from

See merge request hammer/hammer!19

A working h_drop_from which rewrites its underlying sequence as a sequence containing some ignored parsers.

enable h_repeat_n() for CF backends

See merge request hammer/hammer!18

Test/fix h_bits(0, ...)

See merge request hammer/hammer!17

fix string escaping in json output

See merge request hammer/hammer!15

Support custom pretty-printers with USER token types

See merge request hammer/hammer!14

add combinators h_skip, h_seek, h_tell

See merge request hammer/hammer!13

revert changes to examples/base64 - bad merge

See merge request hammer/hammer!12

add const to the pointer arg to h_make_bytes

See merge request hammer/hammer!11

Compiler fixes

See merge request hammer/hammer!10

also allow NULL argument for unamb_sub to mean default