Extend Binary_string::strstr to also take in a const char pointer

One shouldn't have to instantiate a Binary_string every time a strstr
call is needed.

sql/sql_string.cc

@@ -677,33 +677,37 @@ bool String::append_with_prefill(const char *s,uint32 arg_length,
 }
 
 
-int Binary_string::strstr(const Binary_string &s, uint32 offset)
+int Binary_string::strstr(const char *search, uint32 search_length, uint32 offset)
 {
-  if (s.length()+offset <= str_length)
+  if (search_length + offset <= str_length)
   {
-    if (!s.length())
+    if (!search_length)
       return ((int) offset);	// Empty string is always found
 
-    const char *str = Ptr+offset;
-    const char *search=s.ptr();
-    const char *end=Ptr+str_length-s.length()+1;
-    const char *search_end=s.ptr()+s.length();
+    const char *str= Ptr + offset;
+    const char *end= Ptr + str_length - search_length + 1;
+    const char *search_end= search + search_length;
 skip:
     while (str != end)
     {
       if (*str++ == *search)
       {
-	char *i,*j;
-	i=(char*) str; j=(char*) search+1;
-	while (j != search_end)
-	  if (*i++ != *j++) goto skip;
-	return (int) (str-Ptr) -1;
+        char *i= (char*) str;
+        char *j= (char*) search + 1 ;
+        while (j != search_end)
+          if (*i++ != *j++) goto skip;
+        return (int) (str-Ptr) -1;
       }
     }
   }
   return -1;
 }
 
+int Binary_string::strstr(const Binary_string &s, uint32 offset)
+{
+  return strstr(s.ptr(), s.length(), offset);
+}
+
 /*
 ** Search string from end. Offset is offset to the end of string
 */

sql/sql_string.h

@@ -330,6 +330,7 @@ class Binary_string: public Sql_alloc
 
   // Returns offset to substring or -1
   int strstr(const Binary_string &search, uint32 offset=0);
+  int strstr(const char *search, uint32 search_length, uint32 offset=0);
   // Returns offset to substring or -1
   int strrstr(const Binary_string &search, uint32 offset=0);