Committed as obvious.

     libstdc++: Fix several preprocessor directives

     A wrong usage of #define in place of a #error seems to have been 
replicated
     at different places in source files.

     libstdc++-v3/ChangeLog:

             * src/c++11/compatibility-ldbl-facets-aliases.h: Replace 
#define with
             proper #error.
             * src/c++11/locale-inst-monetary.h: Likewise.
             * src/c++11/locale-inst-numeric.h: Likewise.

François