misc: Address issues uncovered with GCC 16 + binutils 2.46 (1/N)

* Funky macro-based definitions for memchr and strstr
   which require an #undef before we use our own in codecs & plugins
 * Return value of of strstr is const

Still have several more warnings and link failure with some plugins
but this is a good start.

Change-Id: Ife1f2d3e6f0e0629e3125a9058abc39c6102f452

lib/rbcodec/codecs/lib/codeclib.c

@@ -38,7 +38,7 @@ int codec_init(void)
     /* codec_get_buffer() aligns the resulting point to MEM_ALIGN_SIZE. */
     mem_ptr = 0;
     mallocbuf = (unsigned char *)ci->codec_get_buffer((size_t *)&bufsize);
-  
+
     return 0;
 }
 
@@ -64,9 +64,9 @@ void* codec_malloc(size_t size)
 
     if (mem_ptr + (long)size > bufsize)
         return NULL;
-    
+
     x=&mallocbuf[mem_ptr];
-    
+
     /* Keep memory aligned to MEM_ALIGN_SIZE. */
     mem_ptr += MEM_ALIGN_UP(size);
 
@@ -136,6 +136,7 @@ int memcmp(const void *s1, const void *s2, size_t n)
     return(ci->memcmp(s1,s2,n));
 }
 
+#undef memchr
 void* memchr(const void *s, int c, size_t n)
 {
     return(ci->memchr(s,c,n));