synclient.c: Replace old index() function with C89-standard strchr()
synclient.c: Replace old index() function with C89-standard strchr()

Fixes Solaris compiler warnings of:
"synclient.c", line 152: warning: implicit function declaration: index
"synclient.c", line 152: warning: improper pointer/integer combination: op "="

Signed-off-by: Alan Coopersmith <ea3248f8c2440b9439894eab21ef26209b22bacf@oracle.com>
Signed-off-by: Peter Hutterer <b9c50af7afa7642f6f854434cda9ffe54ece8b85@who-t.net>

kelnos/xf86-input-synaptics,philipn/xserver-xorg-input-synaptics,RsrchBoy/xserver-xorg-input-synaptics,sencer/synaptics,jiixyj/xf86-input-synaptics,ssaavedra/xf86-input-synaptics,eyko/xf86-input-synaptics,mmonaco/xf86-input-synaptics,Lyude/xf86-input-synaptics,mortehu/xf86-input-synaptics,RsrchBoy/xserver-xorg-input-synaptics,quadpixels/three-finger-dragging,eyko/xf86-input-synaptics,ssaavedra/xf86-input-synaptics,corcoran/xserver-xorg-input-synaptics,philipn/xserver-xorg-input-synaptics,mortehu/xf86-input-synaptics,philipn/xserver-xorg-input-synaptics,gdestuynder/xf86-input-synaptics,jiixyj/xf86-input-synaptics,sencer/synaptics,Lyude/xf86-input-synaptics,corcoran/xserver-xorg-input-synaptics,nanderson94/xf86-input-synaptics,felipejfc/xserver-xorg-input-synaptics,felipejfc/xserver-xorg-input-synaptics,nanderson94/xf86-input-synaptics,gdestuynder/xf86-input-synaptics,kelnos/xf86-input-synaptics,felipejfc/xserver-xorg-input-synaptics,mmonaco/xf86-input-synaptics,quadpixels/three-finger-dragging