PPC and x86 support aligning variables on stack

Originally committed as revision 21865 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -2388,6 +2388,8 @@ elif enabled mips; then
 
 elif enabled ppc; then
 
+    enable local_aligned_8 local_aligned_16
+
     check_asm dcbzl     '"dcbzl 0, 1"'
     check_asm ppc4xx    '"maclhw r10, r11, r12"'
     check_asm xform_asm '"lwzx %1, %y0" :: "Z"(*(int*)0), "r"(0)'
@@ -2422,6 +2424,8 @@ elif enabled sparc; then
 
 elif enabled x86; then
 
+    enable local_aligned_8 local_aligned_16
+
     # check whether EBP is available on x86
     # As 'i' is stored on the stack, this program will crash
     # if the base pointer is used to access it because the