Fix compile warnings only seen on linux-ppc

Most of these are just Altivec or MMX stuff not properly #ifdef'd.  There's
also a unsigned vs signed issue, and one where size - 1 <= size.

mythtv/filters/greedyhdeint/color.c

@@ -231,14 +231,14 @@ static void yv12_to_yuy2_c
 
 #endif
 
+#if HAVE_MMX
 static void yv12_to_yuy2_mmxext
 (const unsigned char *y_src, int y_src_pitch, 
  const unsigned char *u_src, int u_src_pitch, 
  const unsigned char *v_src, int v_src_pitch, 
  unsigned char *yuy2_map, int yuy2_pitch,
  int width, int height, int progressive ) 
 {
-#if HAVE_MMX
     uint8_t *p_line1, *p_line2 = yuy2_map;
     const uint8_t *p_y1, *p_y2 = y_src;
     const uint8_t *p_u = u_src;
@@ -472,14 +472,14 @@ static void yuy2_to_yv12_c
 
 #endif
 
+#if HAVE_MMX
 static void yuy2_to_yv12_mmxext
 (const unsigned char *yuy2_map, int yuy2_pitch,
  unsigned char *y_dst, int y_dst_pitch, 
  unsigned char *u_dst, int u_dst_pitch, 
  unsigned char *v_dst, int v_dst_pitch, 
  int width, int height) 
 {
-#if HAVE_MMX
     const uint8_t *p_line1, *p_line2 = yuy2_map;
     uint8_t *p_y1, *p_y2 = y_dst;
     uint8_t *p_u = u_dst;

mythtv/filters/linearblend/filter_linearblend.c

@@ -32,6 +32,7 @@ typedef struct LBFilter
 void linearBlend(unsigned char *src, int stride);
 void linearBlendMMX(unsigned char *src, int stride);
 void linearBlend3DNow(unsigned char *src, int stride);
+inline void linearBlendAltivec(unsigned char *src, int stride);
 int linearBlendFilterAltivec(VideoFilter *f, VideoFrame *frame, int field);
 
 #ifdef MMX

mythtv/libs/libmythtv/livetvchain.cpp

@@ -247,9 +247,9 @@ void LiveTVChain::GetEntryAt(int at, LiveTVChainEntry &entry) const
     QMutexLocker lock(&m_lock);
 
     int size = m_chain.count();
-    int new_at = (at < 0 || at >= size) ? size - 1 : at;
+    int new_at = (size && (at < 0 || at >= size)) ? size - 1 : at;
 
-    if (new_at >= 0 && new_at <= size)
+    if (size && new_at >= 0 && new_at <= size)
         entry = m_chain[new_at];
     else
     {

mythtv/libs/libmythtv/osdchromakey.cpp

@@ -228,7 +228,7 @@ void ChromaKeyOSD::BlendOrCopy(uint32_t colour, const QRect &rect)
         source += src_stride >> 1;
         dest   += dst_stride >> 1;
 #else
-        for (uint j = 0; j < width; j++)
+        for (int j = 0; j < width; j++)
             dest[j] = (source[j] & MASK) ? source[j] : colour;
         source += src_stride;
         dest   += dst_stride;