build: Remove -Werror from CFLAGS
build: Remove -Werror from CFLAGS

Replace it with a more targetted set of -Werror=[flag] flags, copied from
libsoup: http://git.gnome.org/browse/libsoup/tree/configure.ac?id=f5902fce98ae0314f0d9ca6e544895548c94a456#n339

renatofilho/folks2,GNOME/folks,renatofilho/folks,renatofilho/folks2,GNOME/folks,renatofilho/folks,GNOME/folks,pwithnall/folks,pwithnall/folks,renatofilho/folks2,pwithnall/folks,renatofilho/folks,renatofilho/folks2,renatofilho/folks