Fix cheader_filename in rest-custom.vala
Fix cheader_filename in rest-custom.vala

Automatic generation generates the wrong header filename for RestProxy

tjol/vala-tjol,tjol/vala-tjol,severinh/vala,jessevdk/vala,spidermonkdust/vala,jessevdk/vala,GNOME/vala,playya/vala,phako/vala,flobrosch/vala-fixes,rvu95/vala,Distrotech/vala,Distrotech/vala,Jc2k/vala,kamanashisroy/aroop,flobrosch/vala-fixes,kamanashisroy/aroop,spidermonkdust/vala,flobrosch/vala-fixes,frida/vala,severinh/vala,frida/vala,GNOME/vala,spidermonkdust/vala,xdave/pvala,GNOME/vala,Jc2k/vala,themiwi/vala,GNOME/vala,severinh/vala,jessevdk/vala,themiwi/vala,frida/vala,tjol/vala-tjol,frida/vala,playya/vala,rvu95/vala,themiwi/vala,playya/vala,Distrotech/vala,phako/vala,rvu95/vala,frida/vala,kamanashisroy/aroop