support lzma < 5.1.3alpha

where `lzma_allocator *allocator` isn't declared const

include/providers/lzma.h

@@ -52,12 +52,18 @@ typedef enum
 
 #define lzma_stream_buffer_decode(...) provider_service_lzma->lzma_stream_buffer_decode_ptr (__VA_ARGS__)
 #define lzma_easy_buffer_encode(...)   provider_service_lzma->lzma_easy_buffer_encode_ptr   (__VA_ARGS__)
+#elif LZMA_VERSION < 50010030
+#define lzma_maybe_const
+#endif
+
+#ifndef lzma_maybe_const
+#define lzma_maybe_const const
 #endif
 
 #define DEFINE_lzma_stream_buffer_decode(NAME) NAME( \
     uint64_t *memlimit,                              \
     uint32_t flags,                                  \
-    const lzma_allocator *allocator,                 \
+    lzma_maybe_const lzma_allocator *allocator,      \
     const uint8_t *in,                               \
     size_t *in_pos,                                  \
     size_t in_size,                                  \
@@ -69,7 +75,7 @@ typedef enum
 #define DEFINE_lzma_easy_buffer_encode(NAME) NAME(   \
     uint32_t preset,                                 \
     lzma_check check,                                \
-    const lzma_allocator *allocator,                 \
+    lzma_maybe_const lzma_allocator *allocator,      \
     const uint8_t *in,                               \
     size_t in_size,                                  \
     uint8_t *out,                                    \