Don't undo changes made by commit b70326c6.
Use PKG_CHECK_MODULES to check for GTK+ 2 >= 2.8.0 and to get
{IGE_MAC,GTK}_{CFLAGS,LIBS}.
PKG_CHECK_MODULES renders this macro file useless.
Use PKG_CHECK_MODULES instead to find PROJ CFLAGS and LIBS. Rename
PROJ_LDFLAGS and PROJ_CPPFLAGS to PROJ_LIBS and PROJ_CFLAGS
respectively.