Fix MSVC build: move table_b2a_base64 before inline functions

MSVC doesn't support forward declarations of arrays without explicit
size. Move the table definition before the inline functions that use
it, eliminating the need for a forward declaration.

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: gpshead

Modules/binascii.c

@@ -109,8 +109,8 @@ static const unsigned char table_a2b_base64[] = {
  * This allows the compiler to better optimize the hot loops.
  */
 
-/* Forward declaration for table defined after the inline functions */
-static const unsigned char table_b2a_base64[];
+static const unsigned char table_b2a_base64[] =
+"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
 /* Encode 3 bytes into 4 base64 characters. */
 static inline void
@@ -198,9 +198,6 @@ base64_decode_fast(const unsigned char *in, Py_ssize_t in_len,
     return i * 4;
 }
 
-static const unsigned char table_b2a_base64[] =
-"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
-
 
 static const unsigned short crctab_hqx[256] = {
     0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,