Simplify http_parse_querystring()

Instead of reimplementing URL parameter parsing from scratch, use
url_decode_parameter_name() and url_decode_parameter_value() which are
already provided by Git.

Also, change the return type of http_parse_querystring() to void since
its only caller already ignores the return value.

Signed-off-by: Lukas Fleischer <lfleischer@lfos.de>

html.h

@@ -32,6 +32,6 @@ extern void html_link_close(void);
 extern void html_fileperm(unsigned short mode);
 extern int html_include(const char *filename);
 
-extern int http_parse_querystring(const char *txt, void (*fn)(const char *name, const char *value));
+extern void http_parse_querystring(const char *txt, void (*fn)(const char *name, const char *value));
 
 #endif /* HTML_H */