liblzma: Fix a comment and RC_SYMBOLS_MAX.

The comment didn't match the value of RC_SYMBOLS_MAX and the value
itself was slightly larger than actually needed. The only harm
about this was that memory usage was a few bytes larger.

src/liblzma/rangecoder/range_encoder.h

@@ -19,5 +19,5 @@
 
 
 /// Maximum number of symbols that can be put pending into lzma_range_encoder
-/// structure between calls to lzma_rc_encode(). For LZMA, 52+5 is enough
+/// structure between calls to lzma_rc_encode(). For LZMA, 48+5 is enough
 /// (match with big distance and length followed by range encoder flush).
@@ -23,5 +23,5 @@
 /// (match with big distance and length followed by range encoder flush).
-#define RC_SYMBOLS_MAX 58
+#define RC_SYMBOLS_MAX 53
 
 
 typedef struct {