Show (short) list of possible enum values when an invalid value is encountered (resolves #1318)

All enum errors have (hopefully) been changed to a luax_enumerror, which has a
fixed error message. If additionally a list of valid options is passed, it
lists that in the error message. For every enum error with few options I've
implemented this using a getConstants call.

This solution has been designed specifically to reduce the number of template
instantiations (as I've been told that was a concern). All new template code
happens in places where there already was an instantiation of the relevant
StringMap. Of course there is still std::vector<std::string>...

--HG--
branch : minor

src/modules/graphics/Texture.cpp

@@ -384,6 +384,11 @@ bool Texture::getConstant(TextureType in, const char *&out)
 	return texTypes.find(in, out);
 }
 
+std::vector<std::string> Texture::getConstants(TextureType)
+{
+	return texTypes.getNames();
+}
+
 bool Texture::getConstant(const char *in, FilterMode &out)
 {
 	return filterModes.find(in, out);
@@ -394,6 +399,11 @@ bool Texture::getConstant(FilterMode in, const char *&out)
 	return filterModes.find(in, out);
 }
 
+std::vector<std::string> Texture::getConstants(FilterMode)
+{
+	return filterModes.getNames();
+}
+
 bool Texture::getConstant(const char *in, WrapMode &out)
 {
 	return wrapModes.find(in, out);
@@ -404,6 +414,11 @@ bool Texture::getConstant(WrapMode in, const char *&out)
 	return wrapModes.find(in, out);
 }
 
+std::vector<std::string> Texture::getConstants(WrapMode)
+{
+	return wrapModes.getNames();
+}
+
 StringMap<TextureType, TEXTURE_MAX_ENUM>::Entry Texture::texTypeEntries[] =
 {
 	{ "2d", TEXTURE_2D },