compression: Implement ciscorn's dictionary approach

Massive savings.  Thanks so much @ciscorn for providing the initial
code for choosing the dictionary.

This adds a bit of time to the build, both to find the dictionary
but also because (for reasons I don't fully understand), the binary
search in the compress() function no longer worked and had to be
replaced with a linear search.

I think this is because the intended invariant is that for codebook
entries that encode to the same number of bits, the entries are ordered
in ascending value.  However, I mis-placed the transition from "words"
to "byte/char values" so the codebook entries for words are in word-order
rather than their code order.

Because this price is only paid at build time, I didn't care to determine
exactly where the correct fix was.

I also commented out a line to produce the "estimated total memory size"
-- at least on the unix build with TRANSLATION=ja, this led to a build
time KeyError trying to compute the codebook size for all the strings.
I think this occurs because some single unicode code point ('ァ') is
no longer present as itself in the compressed strings, due to always
being replaced by a word.

As promised, this seems to save hundreds of bytes in the German translation
on the trinket m0.

Testing performed:
 - built trinket_m0 in several languages
 - built and ran unix port in several languages (en, de_DE, ja) and ran
   simple error-producing codes like ./micropython -c '1/0'

1 files changed, 15 insertions, 6 deletions

diff --git a/supervisor/shared/translate.c b/supervisor/shared/translate.c
index 5cd7b8dd8..cc0de7f61 100644
--- a/supervisor/shared/translate.c
+++ b/supervisor/shared/translate.c
@@ -47,13 +47,22 @@ STATIC int put_utf8(char *buf, int u) {
     if(u <= 0x7f) {
         *buf = u;
         return 1;
-    } else if(bigram_start <= u && u <= bigram_end) {
-        int n = (u - 0x80) * 2;
-        // (note that at present, entries in the bigrams table are
-        // guaranteed not to represent bigrams themselves, so this adds
+    } else if(word_start <= u && u <= word_end) {
+        int n = (u - 0x80);
+        size_t off = 0;
+        for(int i=0; i<n; i++) {
+            off += wlen[i];
+        }
+        int ret = 0;
+        // note that at present, entries in the words table are
+        // guaranteed not to represent words themselves, so this adds
         // at most 1 level of recursive call
-        int ret = put_utf8(buf, bigrams[n]);
-        return ret + put_utf8(buf + ret, bigrams[n+1]);
+        for(int i=0; i<wlen[n]; i++) {
+            int len = put_utf8(buf, words[off+i]);
+            buf += len;
+            ret += len;
+        }
+        return ret;
     } else if(u <= 0x07ff) {
         *buf++ = 0b11000000 | (u >> 6);
         *buf   = 0b10000000 | (u & 0b00111111);