Add function compilation

Functions are compiled in the most naiive way right now. I want to fix
up how scope lookups are done before it becomes too much to update.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/syn/parser.y

@@ -6,6 +6,8 @@
 %left '*' '/'
 %left '+' '-'
 
+%avoid_insert "NUM" "SYM" "STRING" "||" "&&" "<" ">" "<=" ">=" "!=" "==" "+" "-" "*" "/" "{"
+
 %%
 
 Body -> Result<Vec<Stmt>>: