Fix a small parsing edge case issue

Author: mgreter

src/parser.cpp

@@ -1460,7 +1460,7 @@ namespace Sass {
     if (lex< sequence< dimension, optional< sequence< exactly<'-'>, negate< digit > > > > >())
     { return SASS_MEMORY_NEW(ctx.mem, Textual, pstate, Textual::DIMENSION, lexed); }
 
-    if (lex< sequence< static_component, one_plus< identifier > > >())
+    if (lex< sequence< static_component, one_plus< strict_identifier > > >())
     { return SASS_MEMORY_NEW(ctx.mem, String_Constant, pstate, lexed); }
 
     if (lex< number >())

src/prelexer.cpp

@@ -108,6 +108,16 @@ namespace Sass {
              >(src);
     }
 
+    // Match CSS identifiers.
+    const char* strict_identifier(const char* src)
+    {
+      return sequence<
+               one_plus < strict_identifier_alpha >,
+               zero_plus < strict_identifier_alnum >
+               // word_boundary not needed
+             >(src);
+    }
+
     // Match CSS identifiers.
     const char* identifier(const char* src)
     {

src/prelexer.hpp

@@ -195,6 +195,7 @@ namespace Sass {
     const char* identifier(const char* src);
     const char* identifier_alpha(const char* src);
     const char* identifier_alnum(const char* src);
+    const char* strict_identifier(const char* src);
     const char* strict_identifier_alpha(const char* src);
     const char* strict_identifier_alnum(const char* src);
     // Match a CSS unit identifier.