Nuke as many warnings as possible, and several globals as well

- Warnings completely suppressed for the included TinyXML and gzstream libraries
- Parentheses warnings are now errors, since there were several that looked like bugs
- Ditto for dangling else warnings

Some of these warnings were actually bugs:
- Town wandering monsters would have never spawned, because the code to do so was accidentally nested within a check for overall_mode == MODE_OUTDOORS
---> boe.monster.cpp, lines 105-137
- Monster's behaviour with respect to elemental fields did not correctly depend on their immunities (this is the same precedence issue Sylae messed up fixing in the Windows code)
---> boe.monsters.cpp, lines 345-359
- Display of damage blocked by armour appeared to be incorrect (needs verification)
---> boe.newgraph.cpp, line 1079
- Three-choice dialogs probably weren't dealing with unusual button types correctly, though that's a minor point since they aren't expected to use such buttons

osx/tools/graphtool.cpp

@@ -62,7 +62,7 @@ void init_graph_tool(){
 	}
 	delete[] fbuf;
 	delete[] vbuf;
-	int i,j;
+	int i;
 	// TODO: The duplication of location here shouldn't be necessary
 	static const location pat_offs[17] = {
 		location{0,3}, location{1,1}, location{2,1}, location{2,0},
@@ -240,7 +240,7 @@ std::vector<snippet_t> draw_string_sel(sf::RenderTarget& dest_window,RECT dest_r
 	return params.snippets;
 }
 
-void push_snippets(size_t start, size_t end, text_params_t& options, size_t& iHilite, const std::string& str, location loc) {
+static void push_snippets(size_t start, size_t end, text_params_t& options, size_t& iHilite, const std::string& str, location loc) {
 	std::vector<hilite_t>& hilites = options.hilite_ranges;
 	std::vector<snippet_t>& snippets = options.snippets;
 	// Check if we have any hilites on this line.