io: Always use unbuffered input

Before, we often used unbuffered input via the lzma or gzip handlers,
more or less inadvertently.

Change the default file handlers from buffered (stdc FILE) to unbuffered
(POSIX fds).

python/generator.py

@@ -298,6 +298,7 @@ deprecated_funcs = {
     'namePush': True,
     'nodePop': True,
     'nodePush': True,
+    'xmlCheckFilename': True,
     'xmlCheckLanguageID': True,
     'xmlCleanupCharEncodingHandlers': True,
     'xmlCleanupGlobals': True,
@@ -305,6 +306,7 @@ deprecated_funcs = {
     'xmlDecodeEntities': True,
     'xmlDictCleanup': True,
     'xmlEncodeEntities': True,
+    'xmlFileMatch': True,
     'xmlHandleEntity': True,
     'xmlInitCharEncodingHandlers': True,
     'xmlInitGlobals': True,