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/scan_html.c

@@ -3,7 +3,7 @@
 #include "haveinline.h"
 #include "case.h"
 
-unsigned int scan_html(const char *src,char *dest,unsigned int *destlen) {
+unsigned long scan_html(const char *src,char *dest,unsigned long *destlen) {
   register const unsigned char* s=(const unsigned char*) src;
   unsigned long written=0,i;
   for (i=0; s[i]; ++i) {