Add -fpermissive to linux standard c++ option define in linux.cf

Remove from individual Imakefiles.

Also, remove '#if 0' block in linux.cf, and remove empty
LinuxMachineDefines. This should be working correctly.  If not, let me
know.

cde/programs/nsgmls/Imakefile

@@ -77,7 +77,7 @@ STLIBCENV =
 M4 = /bin/m4
 #endif
 
-#ifdef LinuxArchitecture
+#if defined(LinuxArchitecture(
 
 /*
  * put cpp directives here rather than in CXXDEFINES because
@@ -95,8 +95,6 @@ CXXTEMPLATEFLAGS =
 
 M4 = /usr/bin/m4
 
-CXXEXTRA_DEFINES = -fpermissive
-
 #endif
 
 #if defined(RsArchitecture)