Boot core library from image rather than source

This should speed up start time and reduce malloc/free
usage to about 15% of what is what previously for startup.
The current cost is slightly larger binary as the representaion
of the image is currently less compact than source code.

tools/amalg.janet

@@ -71,5 +71,6 @@
 (each h headers (dofile h))
 (each s sources (dofile s))
 
-# Relies on this file being built
+# Relies on these files being built
 (dofile "build/core.gen.c")
+(dofile "build/core_image.c")

tools/marshal_core.janet

@@ -1,21 +0,0 @@
-# Tool to dump a marshalled version of the janet core to stdout. The
-# image should eventually allow janet to be started from a pre-compiled
-# image rather than recompiled every time from the embedded source. More
-# work will go into shrinking the image (it isn't currently that large but
-# could be smaller), creating the mechanism to load the image, and modifying
-# the build process to compile janet with a built image rather than
-# embedded source.
-
-# Get image. This image contains as much of the core library and documentation that
-# can be written to an image (no cfunctions, no abstracts (stdout, stdin, stderr)),
-# everything else goes. Cfunctions and abstracts will be referenced from a register
-# table which will be generated on janet startup.
-(def image (let [env-pairs (pairs (env-lookup *env*))
-                 essential-pairs (filter (fn [[k v]] (or (cfunction? v) (abstract? v))) env-pairs)
-                 lookup (table ;(mapcat identity essential-pairs))
-                 reverse-lookup (invert lookup)]
-             (marshal (table/getproto *env*) reverse-lookup)))
-
-# Write image
-(file/write stdout image)
-(file/flush stdout)