x86: Pass -Worphan-labels to yasm

Makes it easier to detect typos.

common/x86/dct-a.asm

@@ -675,7 +675,7 @@ cglobal add16x16_idct_dc, 2,3,8
     mova        m6, [pw_pixel_max]
     mova        m7, [pd_32]
     pxor        m5, m5
-.loop
+.loop:
     mova        m3, [r1]
     paddd       m3, m7
     psrad       m3, 6         ; dc0   0 dc1   0 dc2   0 dc3   0

common/x86/deblock-a.asm

@@ -621,7 +621,7 @@ cglobal deblock_v_luma_intra, 4,7,16
     mov     r6, 2
     mova    m0, [pw_2]
     LOAD_AB aa, bb, r2d, r3d
-.loop
+.loop:
     mova    p2, [r4+r1]
     mova    p1, [r4+2*r1]
     mova    p0, [r4+r5]
@@ -671,7 +671,7 @@ cglobal deblock_h_luma_intra, 4,7,16
     add     r4, r0     ; pix+4*stride
     mov     r6, 2
     mova    m0, [pw_2]
-.loop
+.loop:
     movu    q3, [r0-8]
     movu    q2, [r0+r1-8]
     movu    q1, [r0+r1*2-8]

common/x86/pixel-a.asm

@@ -205,7 +205,7 @@ cglobal pixel_ssd_%1x%2, 4,7,6
     mov    r4d, %%n
 %endif
     pxor    m0, m0
-.loop
+.loop:
     mova    m1, [r0]
     mova    m2, [r0+offset0_1]
     mova    m3, [r0+offset0_2]

configure

@@ -733,6 +733,7 @@ if [ $asm = auto -a \( $ARCH = X86 -o $ARCH = X86_64 \) ] ; then
         echo "If you really want to compile without asm, configure with --disable-asm."
         exit 1
     fi
+    ASFLAGS="$ASFLAGS -Worphan-labels"
     define HAVE_MMX
     if cc_check '' -mpreferred-stack-boundary=5 ; then
         CFLAGS="$CFLAGS -mpreferred-stack-boundary=5"