maint: Clean up various usages of #ifdef. * randmtzig.c: Use #ifdef rather than just #if. * EditControl.h : Use '#if ! defined' rather than '#ifndef' in guard block to match Octave style. * dialog.cc, settings-dialog.cc: Add FIXME notes about questionable use of #if mechanism. * file-editor-tab.cc, Array-b.cc, Array-ch.cc, Array-d.cc, Array-f.cc, Array-i.cc, Array-s.cc, MatrixType.h, quit.h, lo-sysdep.cc, lo-cutils.c, oct-alloc.h, oct-shlib.cc, sparse-sort.h: #define HAVE_XXX macros to 1, not just empty but defined. * octave-txt-lexer.h, octave-cmd.h, octave-preserve-stream-state.h, txt-eng.h, zfstream.h, oct-conf-features.h, oct-conf.h: Use octave_ namespace prefix on name of #define used to prevent multiple inclusion of headers. * parser.h, webinfo.h, ov-oncleanup.h, op-int.h, display-available.h, shared-fcns.h: Add #define guard to prevent multiple inclusion. * quadcc.cc: use all capitals for #define MIN_CQUAD_HEAPSIZE. * ov-intx.h: Add note that this file must not use guard #define. * eigs-base.h, randmtzig.h: Write '! defined' rather than '!defined'. * file-ops.cc, oct-sparse.h: Use parentheses around complex #if tests. * oct-syscalls.cc, oct-base64.cc, statdefs.h: Indent #ifdef blocks correctly. * oct-conf-post.in.h: Use "! defined". Define macros to 1, not just empty but defined.

--- a/libinterp/corefcn/quadcc.cc	Sat Feb 06 19:18:59 2016 -0500
+++ b/libinterp/corefcn/quadcc.cc	Sat Feb 06 18:22:32 2016 -0800
@@ -38,7 +38,7 @@
 #define DEBUG_QUADCC 0
 
 // Define the minimum size of the interval heap.
-#define min_cquad_heapsize  200
+#define MIN_CQUAD_HEAPSIZE  200
 
 // Data of a single interval.
 typedef struct
@@ -1615,8 +1615,8 @@
   else
     nivals = 1 + args(4).numel ();
 
-  int cquad_heapsize = (nivals >= min_cquad_heapsize ? nivals + 1
-                                                     : min_cquad_heapsize);
+  int cquad_heapsize = (nivals >= MIN_CQUAD_HEAPSIZE ? nivals + 1
+                                                     : MIN_CQUAD_HEAPSIZE);
   // The interval heap.
   OCTAVE_LOCAL_BUFFER (cquad_ival, ivals, cquad_heapsize);
   OCTAVE_LOCAL_BUFFER (double, iivals, cquad_heapsize);