linux: Use installed X11 header files rather than requiring /imports/x11/include

With this patch, it is no longer neccessary to create the
/imports/x11/include/X11 symlink...

Also, remove the include of xfree86.cf from linux.cf, and define our
own DefaultCCOptions.  Setup to use only -ansi, not -pendantic.

cde/config/cf/linux.cf

@@ -1,10 +1,5 @@
 XCOMM platform:  $TOG: linux.cf /main/47 1998/04/17 11:32:51 mgreess $
 
-/* To reduce the number of warnings generated by X11 and Motif headers that
-   dislike -ansi and -pedantic we can include them with -isystem instead of
-   -I, this tells GCC to treat them as system includes out of our control */
-#define TopXInclude -isystem$(TOP)/imports/x11/include
-
 #ifndef OSName
 # define OSName			DefaultOSName
 #endif
@@ -65,6 +60,8 @@ XCOMM binutils:  (LinuxBinUtilsMajorVersion)
 # endif
 #endif
 
+#define UseInstalledX11         YES
+
 #define BuildLibPathVar   	LD_LIBRARY_PATH
 #define HasGcc			YES
 #define HasGcc2			YES
@@ -129,6 +126,8 @@ XCOMM binutils:  (LinuxBinUtilsMajorVersion)
 
 #define LinuxLocaleDefines	/**/
 
+#define DefaultCCOptions -ansi
+
 XCOMM If you have the tirpc library on your system, and you have the
 XCOMM libtirpc-dev installed, then define HasTIRPCLib to YES in either
 XCOMM your host.def or site.def file.  Using the tirpc lib should
@@ -297,4 +296,3 @@ DependFileName::                                                        @@@@\
 #define TtClientDepLibs $(DEPTTLIB) $(DEPXTOOLLIB) $(DEPXLIB)
 
 #include <lnxLib.rules>
-#include <xfree86.cf>

cde/config/imake/Makefile.ini

@@ -11,7 +11,7 @@
 BOOTSTRAPCFLAGS = 
 CC = cc
 CDEBUGFLAGS = -O
-INCLUDES = -I../../include -I../../imports/x11/include/X11
+INCLUDES = -I../../include -I/usr/include/X11 -I../../imports/x11/include/X11
 CFLAGS = $(BOOTSTRAPCFLAGS) $(CDEBUGFLAGS) $(INCLUDES)
 SHELL = /bin/sh
 RM = rm -f