PARQUET-739: Don't use a static buffer for data accessed by multiple …

…threads

I am hitting this problem at another location too.

Author: Deepak Majeti <deepak.majeti@hpe.com>

Closes apache#177 from majetideepak/PARQUET-739 and squashes the following commits:

85a73f1 [Deepak Majeti] PARQUET-739

cpp/src/parquet/util/bit-stream-utils.inline.h

@@ -149,7 +149,7 @@ inline int BitReader::GetBatch(int num_bits, T* v, int batch_size) {
     byte_offset += num_unpacked * num_bits / 8;
   } else {
     const int buffer_size = 1024;
-    static uint32_t unpack_buffer[buffer_size];
+    uint32_t unpack_buffer[buffer_size];
     while (i < batch_size) {
       int unpack_size = std::min(buffer_size, batch_size - i);
       int num_unpacked = unpack32(reinterpret_cast<const uint32_t*>(buffer + byte_offset),