Increase maximum window size

* Maximum window size in 32-bit mode is 1GB, since allocations for 2GB fail
  on my Mac.
* Maximum window size in 64-bit mode is 2GB, since that is the largest
  power of 2 that works with the overflow prevention.
* Allow `--long=windowLog` to set the window log, along with
  `--zstd=wlog=#`. These options also set the window size during
  decompression, but don't override `--memory=#` if it is set.
* Present a helpful error message when the window size is too large during
  decompression.
* The long range matcher defaults to a hash log 7 less than the window log,
  which keeps it at 20 for window log 27.
* Keep the default long range matcher window size and the default maximum
  window size at 27 for the API and CLI.
* Add tests that use the maximum window size and hash size for compression
  and decompression.

lib/zstd.h

@@ -376,8 +376,8 @@ ZSTDLIB_API size_t ZSTD_DStreamOutSize(void);   /*!< recommended size for output
 #define ZSTD_MAGIC_SKIPPABLE_START  0x184D2A50U
 #define ZSTD_MAGIC_DICTIONARY       0xEC30A437   /* v0.7+ */
 
-#define ZSTD_WINDOWLOG_MAX_32  27
-#define ZSTD_WINDOWLOG_MAX_64  27
+#define ZSTD_WINDOWLOG_MAX_32  30
+#define ZSTD_WINDOWLOG_MAX_64  31
 #define ZSTD_WINDOWLOG_MAX    ((unsigned)(sizeof(size_t) == 4 ? ZSTD_WINDOWLOG_MAX_32 : ZSTD_WINDOWLOG_MAX_64))
 #define ZSTD_WINDOWLOG_MIN     10
 #define ZSTD_HASHLOG_MAX       MIN(ZSTD_WINDOWLOG_MAX, 30)
@@ -941,7 +941,9 @@ typedef enum {
                               * Special: value 0 means "do not change cLevel". */
     ZSTD_p_windowLog,        /* Maximum allowed back-reference distance, expressed as power of 2.
                               * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
-                              * Special: value 0 means "do not change windowLog". */
+                              * Special: value 0 means "do not change windowLog".
+                              * Note: Using a window size greater than ZSTD_MAXWINDOWSIZE_DEFAULT (default: 2^27)
+                              * requires setting the maximum window size at least as large during decompression. */
     ZSTD_p_hashLog,          /* Size of the probe table, as a power of 2.
                               * Resulting table size is (1 << (hashLog+2)).
                               * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
@@ -1009,7 +1011,7 @@ typedef enum {
                           * Larger values increase memory usage and compression ratio, but decrease
                           * compression speed.
                           * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
-                          * (default: 20). */
+                          * (default: windowlog - 7). */
     ZSTD_p_ldmMinMatch,  /* Minimum size of searched matches for long distance matcher.
                           * Larger/too small values usually decrease compression ratio.
                           * Must be clamped between ZSTD_LDM_MINMATCH_MIN