pppd: tune Linux config defaults for OpenWrt

This patch adjusts a number defaults to properly match the OpenWrt environment.
It is not intended for upstream.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

--- a/pppd/Makefile.linux
+++ b/pppd/Makefile.linux
@@ -48,7 +48,7 @@ MPPE=y
 # Uncomment the next line to include support for PPP packet filtering.
 # This requires that the libpcap library and headers be installed
 # and that the kernel driver support PPP packet filtering.
-FILTER=y
+#FILTER=y
 
 # Uncomment the next line to enable multilink PPP (enabled by default)
 # Linux distributions: Please leave multilink ENABLED in your builds
@@ -58,7 +58,7 @@ HAVE_MULTILINK=y
 # Uncomment the next line to enable the TDB database (enabled by default.)
 # If you enable multilink, then TDB is automatically enabled also.
 # Linux distributions: Please leave TDB ENABLED in your builds.
-USE_TDB=y
+#USE_TDB=y
 
 HAS_SHADOW=y
 #USE_PAM=y
@@ -80,7 +80,7 @@ MAXOCTETS=y
 
 INCLUDE_DIRS= -I../include
 
-COMPILE_FLAGS= -DHAVE_PATHS_H -DIPX_CHANGE -DHAVE_MMAP
+COMPILE_FLAGS= -DHAVE_PATHS_H -DHAVE_MMAP
 
 CFLAGS= $(COPTS) $(COMPILE_FLAGS) $(INCLUDE_DIRS) '-DDESTDIR="@DESTDIR@"'
 
@@ -120,10 +120,10 @@ CFLAGS   += -DHAS_SHADOW
 #LIBS     += -lshadow $(LIBS)
 endif
 
-ifneq ($(wildcard /usr/include/crypt.h),)
+#ifneq ($(wildcard /usr/include/crypt.h),)
 CFLAGS  += -DHAVE_CRYPT_H=1
 LIBS	+= -lcrypt
-endif
+#endif
 
 ifdef USE_LIBUTIL
 CFLAGS	+= -DHAVE_LOGWTMP=1