remove special case stralloc textcode functions

write generic stralloc and array textcode wrapper functions
change textcode API to use long instead of int
add cescape fmt and scan functions to textcode
add fmt_foldwhitespace to textcode

textcode/fmt_html.c

@@ -3,7 +3,7 @@
 #include "str.h"
 #include "haveinline.h"
 
-unsigned int fmt_html(char* dest,const char* src,unsigned int len) {
+unsigned long fmt_html(char* dest,const char* src,unsigned long len) {
   register const unsigned char* s=(const unsigned char*) src;
   unsigned long written=0,i;
   const char* seq;