Use character literals 'c' rather than string literals "c" when possible. Better performance when string constructor isn't required. * Figure.cc, __init_qt__.cc, files-dock-widget.cc, file-editor-tab.cc, file-editor.cc, octave-qscintilla.cc, main-window.cc, octave-dock-widget.cc, octave-qt-link.cc, parser.cc, webinfo.cc, resource-manager.cc, settings-dialog.cc, workspace-view.cc, __magick_read__.cc, balance.cc, debug.cc, dynamic-ld.cc, ft-text-renderer.cc, gl-render.cc, gl2ps-print.cc, graphics.cc, hook-fcn.h, input.cc, load-path.cc, load-save.cc, ls-hdf5.cc, oct-hist.cc, oct-stream.cc, pager.cc, pr-output.cc, qz.cc, symtab.cc, symtab.h, tril.cc, __delaunayn__.cc, __init_fltk__.cc, __voronoi__.cc, audioread.cc, ccolamd.cc, colamd.cc, convhulln.cc, ov-base-int.cc, ov-base-mat.cc, ov-base-scalar.cc, ov-base.cc, ov-bool-mat.cc, ov-cell.cc, ov-class.cc, ov-classdef.cc, ov-colon.cc, ov-complex.cc, ov-cx-mat.cc, ov-fcn-handle.cc, ov-fcn-inline.cc, ov-fcn.h, ov-flt-cx-mat.cc, ov-flt-re-mat.cc, ov-java.cc, ov-oncleanup.cc, ov-range.cc, ov-re-mat.cc, ov-re-sparse.cc, ov-str-mat.cc, ov-struct.cc, ov-usr-fcn.cc, ov.cc, octave.cc, bp-table.cc, jit-ir.cc, jit-ir.h, jit-typeinfo.cc, pt-funcall.cc, pt-idx.cc, pt-pr-code.cc, pt.h, Array.cc, CDiagMatrix.cc, CMatrix.cc, CNDArray.cc, CRowVector.cc, CSparse.cc, Range.cc, boolSparse.cc, dDiagMatrix.cc, dMatrix.cc, dNDArray.cc, dRowVector.cc, dSparse.cc, fCDiagMatrix.cc, fCMatrix.cc, fCNDArray.cc, fCRowVector.cc, fDiagMatrix.cc, fMatrix.cc, fNDArray.cc, fRowVector.cc, idx-vector.cc, intNDArray.cc, CollocWt.cc, DASPK.cc, DASRT.cc, DASSL.cc, LSODE.cc, oct-time.cc, cmd-hist.cc, kpse.cc, lo-array-errwarn.cc, lo-regexp.cc, lo-utils.cc, str-vec.cc, url-transfer.cc, main-cli.cc, main-gui.cc, mkoctfile.in.cc: Replace 1-character string literals "c" with the character literal 'c'.

--- a/liboctave/util/cmd-hist.cc	Fri Jul 28 11:45:07 2017 -0700
+++ b/liboctave/util/cmd-hist.cc	Fri Jul 28 15:40:00 2017 -0700
@@ -129,7 +129,7 @@
           beg++;
         else
           {
-            size_t end = control_arg.find (":", beg);
+            size_t end = control_arg.find (':', beg);
 
             if (end == std::string::npos)
               end = len;
@@ -169,7 +169,7 @@
     if (history_control & HC_IGNDUPS)
       {
         if (retval.length () > 0)
-          retval.append (":");
+          retval += ':';
 
         retval.append ("ignoredups");
       }
@@ -177,7 +177,7 @@
     if (history_control & HC_ERASEDUPS)
       {
         if (retval.length () > 0)
-          retval.append (":");
+          retval += ':';
 
         retval.append ("erasedups");
       }