input: Controller unique mapping (preliminary)

Add ini option `unique_mapping` which makes controller mappings unique to the physical port the controller is connected to.
Calculates a uint32_t unique_hash for each device during enumeration.

Co-authored-by: Martin Donlon <github-martin@donlons.com>

str_util.cpp

@@ -31,4 +31,17 @@ char *strncpyz(char *dest, size_t dest_size, const char *src, size_t num)
 char *strcpyz(char *dest, size_t dest_size, const char *src)
 {
 	return strncpyz(dest, dest_size, src, dest_size - 1);
+}
+
+unsigned int str_hash(const char *s, unsigned int initial)
+{
+	unsigned int hash = initial;
+	int c;
+
+	while( c = *s++ )
+	{
+		hash = ((hash << 5) + hash) + c;
+	}
+
+	return hash;
 }