Initialise gct_size with a default value, to prevent a build failure

 with -O2.

--- giftrans-1.12.2.orig/giftrans.c

+++ giftrans-1.12.2/giftrans.c

@@ -383,7 +383,7 @@

 FILE	*dest;

 {

 	unsigned char	buffer[3*256],lsd[7],gct[3*256],gce[5];

-	unsigned int	cnt,cols,size,gct_size,gct_delay,gce_present;

+	unsigned int	cnt,cols,size,gct_size=0,gct_delay,gce_present;

 	struct entry	*rgbptr;