Rearrange mmx_t union to make gcc happy.

When we initialize with an unsigned long long using:
  mmx_t var = { 0x8000000000000000ULL };
It makes the compiler unhappy because it tries to
assign the mmx_t's .q which is of type long long
and this number is too large to be represented in
a long long. By moving the unsigned long long .uq to
be first in the union the compiler will try that
first and not give a narrowing complaint.
An alternative in C99 code is:
  mmx_t var = { .uq = 0x8000000000000000ULL };
But in C++ the only alternative is:
  mmx_t var;
  var.uq = 0x8000000000000000ULL;
Which to my eyes is less elegant.

mythtv/libs/libmythbase/ffmpeg-mmx.h

@@ -31,9 +31,14 @@
  * values by ULL, lest they be truncated by the compiler)
  */
 
+/* Note: moved uq to be first so we can initialize with ULL
+ * in C++11 code without narrowing complaints or use of gcc
+ * extensions. -- Daniel Kristjansson 2012-12-13
+ */
+
 typedef        union {
-        long long               q;      /* Quadword (64-bit) value */
         unsigned long long      uq;     /* Unsigned Quadword */
+        long long               q;      /* Quadword (64-bit) value */
         int                     d[2];   /* 2 Doubleword (32-bit) values */
         unsigned int            ud[2];  /* 2 Unsigned Doubleword */
         short                   w[4];   /* 4 Word (16-bit) values */