Janet 1.9.0

This release brings a lot of updates, mainly the beta net/ module that brings asynchronous, non-blocking socket networking to Janet's core. As per usual, check the changelog for updates and happy hacking!

• Add :ldflags option to many jpm declare functions.
• Add errorf to core.
• Add lenprefix combinator to PEGs.
• Add %M, %m, %N, and %n formatters to formatting functions. These are the
  same as %Q, %q, %P, and %p, but will not truncate long values.
• Add fiber/root.
• Add beta net/ module to core for socket based networking.
• Add the parse function to parse strings of source code more conveniently.
• Add jpm rule-tree subcommand.
• Add --offline flag to jpm to force use of the cache.
• Allow sending pointers and C functions across threads via thread/send.
• Fix bug in getline.
• Add sh-rule and sh-phony to jpm's dialect of Janet.
• Change C api's janet_formatb -> janet_formatbv, and add new function janet_formatb to C api.
• Add edefer macro to core.
• A struct/table literal/constructor with duplicate keys will use the last value given.
  Previously, this was inconsistent between tables and structs, literals and constructor functions.
• Add debugger to core. The debugger functions are only available
  in a debug repl, and are prefixed by a ..
• Add sort-by and sorted-by to core.
• Support UTF-8 escapes in strings via \uXXXX or \UXXXXXX.
• Add math/erf
• Add math/erfc
• Add math/log1p
• Add math/next
• Add os/umask
• Add os/perm-int
• Add os/perm-string
• Add :int-permissions option for os/stat.
• Add jpm repl subcommand, as well as post-deps macro in project.janet files.
• Various bug fixes.