tif driver create() does not honor WEBP_LEVEL or WEBP_LOSSLESS

[tbonfort]

#include <gdal.h>
#include <gdal_utils.h>

int main(int argc, char **argv) {
	GDALAllRegister();
	GDALDriverH tif = GDALGetDriverByName("GTIFF");
	char **opts=calloc(5,sizeof(char*));
	opts[0]="WEBP_LEVEL=95";
	opts[1]="TILED=YES";
	opts[2]="COMPRESS=WEBP";
	opts[3]="BIGTIFF=YES";
	GDALDatasetH ds = GDALCreate(tif,"foo.tif",1024,1024,4,GDT_Byte,opts);
	char *buf=malloc(1024*1024*4);
	for(int i=0;i<1024;i++) {
		for(int j=0;j<1024;j+=4) {
			char *pix = buf+i*1024+j;
			pix[0]=i;
			pix[1]=i;
			pix[2]=i;
			pix[3]=255;
		}
	}
	GDALDatasetRasterIO(ds,GF_Write,0,0,1024,1024,buf,1024,1024,GDT_Byte,4,NULL,4,1024*4,1);
	GDALClose(ds);
}

Running this code after changing the value of WEBP_LEVEL will result in an indentical file being created, i.e. WEBP_LEVEL is ignored.