don't unkebabify -> in symbols (it's -> from C)

example/test-list.sex

@@ -38,6 +38,7 @@
      (printf "Size of the list: %zu\n" (length-list-int l))
      ,(list-for-each '((printf "%d " v) l v))
      (printf "\n")
+     (printf "%zu\n" l->next)
      0)
 
 (pub fn segs-renderer* create-renderer ())

sexc.scm

@@ -9,6 +9,7 @@
         fmt
         fmt-c
         getopt-long
+        regex
         srfi-1                          ; list routines
         tree)
 
@@ -22,7 +23,8 @@
     ((-=) sym)
     (else
      (string->symbol
-      (string-translate (symbol->string sym) #\- #\_)))))
+      (string-substitute "-(?!>)" "_"
+                         (symbol->string sym) #t)))))
 
 (define (atom-to-fmt-c atom)
   (case atom