[string.classes] Avoid special characters in stable labels

and rename [string.comparison] to [string.cmp] per convention

Author: jensmaurer

source/strings.tex

@@ -1760,7 +1760,7 @@
 
 \rSec3[string.modifiers]{Modifiers}
 
-\rSec4[string.op+=]{\tcode{basic_string::operator+=}}
+\rSec4[string.op.append]{\tcode{basic_string::operator+=}}
 
 \indexlibrarymember{operator+=}{basic_string}%
 \begin{itemdecl}
@@ -3141,7 +3141,7 @@
 
 \indexlibrary{\idxcode{basic_string}}
 
-\rSec3[string.op+]{\tcode{operator+}}
+\rSec3[string.op.plus]{\tcode{operator+}}
 
 \indexlibrarymember{operator+}{basic_string}%
 \begin{itemdecl}
@@ -3319,7 +3319,7 @@
 \end{codeblock}
 \end{itemdescr}
 
-\rSec3[string.comparison]{Non-member comparison functions}
+\rSec3[string.cmp]{Non-member comparison functions}
 \begin{itemdecl}
 template<class charT, class traits, class Allocator>
   bool operator==(const basic_string<charT, traits, Allocator>& lhs,

source/xrefdelta.tex

@@ -176,12 +176,14 @@
 \movedxref{string.find.last.of}{string.find}
 \movedxref{string.find.first.not.of}{string.find}
 \movedxref{string.find.last.not.of}{string.find}
-\movedxref{string.operator==}{string.comparison}
-\movedxref{string.op!=}{string.comparison}
-\movedxref{string.op<}{string.comparison}
-\movedxref{string.op>}{string.comparison}
-\movedxref{string.op<=}{string.comparison}
-\movedxref{string.op>=}{string.comparison}
+\movedxref{string.op+=}{string.op.append}
+\movedxref{string.op+}{string.op.plus}
+\movedxref{string.operator==}{string.cmp}
+\movedxref{string.op!=}{string.cmp}
+\movedxref{string.op<}{string.cmp}
+\movedxref{string.op>}{string.cmp}
+\movedxref{string.op<=}{string.cmp}
+\movedxref{string.op>=}{string.cmp}
 
 % Deprecated features.
 %\deprxref{old.label}  (if moved to depr.old.label, otherwise use \movedxref)