parser: Introduce new input API

- xmlInputCreateUrl
- xmlInputCreateMemory
- xmlInputCreateString
- xmlInputCreateFd
- xmlInputCreateIO
- xmlInputSetEncoding

These functions don't take a parser context and work on xmlParserInputs,
replacing functions working on xmlParserInputBuffers.

xmlInputCreateUrl and xmlInputSetEncoding offer fine-grained error
handling.

Several XML_INPUT_* flags offer additional control.

include/libxml/parserInternals.h

@@ -356,6 +356,29 @@ XMLPUBFUN xmlParserInputPtr
 XMLPUBFUN xmlParserInputPtr
 			xmlNewInputStream	(xmlParserCtxtPtr ctxt);
 
+/**
+ * New input API
+ */
+
+#define XML_INPUT_BUF_STATIC		(1u << 1)
+#define XML_INPUT_BUF_ZERO_TERMINATED	(1u << 2)
+#define XML_INPUT_UNZIP                 (1u << 3)
+
+XMLPUBFUN int
+xmlInputCreateUrl(const char *url, int flags, xmlParserInputPtr *out);
+XMLPUBFUN xmlParserInputPtr
+xmlInputCreateMemory(const char *url, const void *mem, size_t size,
+                     int flags);
+XMLPUBFUN xmlParserInputPtr
+xmlInputCreateString(const char *url, const char *str, int flags);
+XMLPUBFUN xmlParserInputPtr
+xmlInputCreateFd(const char *url, int fd, int flags);
+XMLPUBFUN xmlParserInputPtr
+xmlInputCreateIO(const char *url, xmlInputReadCallback ioRead,
+                 xmlInputCloseCallback ioClose, void *ioCtxt, int flags);
+XMLPUBFUN int
+xmlInputSetEncoding(xmlParserInputPtr input, const char *encoding);
+
 /**
  * Namespaces.
  */