inspired from a fix from glibc:
http://www.sourceware.org/ml/libc-alpha/2011-12/msg00091.html

--- kBuild-0.1.9998/./src/sed/lib/regex_internal.c~	2012-11-25 17:35:24.000000000 +0200
+++ kBuild-0.1.9998/./src/sed/lib/regex_internal.c	2012-11-25 19:16:31.260977775 +0200
@@ -781,7 +781,7 @@
 }
 
 static unsigned char
-internal_function __attribute ((pure))
+internal_function
 re_string_fetch_byte_case (re_string_t *pstr)
 {
   if (BE (!pstr->mbs_allocated, 1))