glsl: new glsl_strtod() wrapper to fix decimal point interpretation

We always want to use '.' as the decimal point.

See http://bugs.freedesktop.org/show_bug.cgi?id=24531

NOTE: this is a candidate for the 7.10 branch.

src/glsl/SConscript

@@ -76,6 +76,7 @@ sources = [
     'opt_swizzle_swizzle.cpp',
     'opt_tree_grafting.cpp',
     's_expression.cpp',
+    'strtod.c',
 ]
 
 glsl = env.ConvenienceLibrary(