Android update and small improvements

-fixed code do cross compiling to android
-fixed build with GCC (workaround)
-added little benchmark
-several small fixes
-updated meson build (demos building, working with GCC, LDC and DMD)
-added some meson options
-added ImGUI bind for OpenGL3

meson.build

@@ -23,6 +23,8 @@ tests_src = [
 ]
 
 betterC_opt = get_option('betterC')
+BuildDemos_opt = get_option('BuildDemos')
+LTO_otp = get_option('LTO')
 
 comp = meson.get_compiler('d')
 
@@ -31,16 +33,41 @@ comp_id = comp.get_id()
 args = []
 link_args = []
 
+if comp_id == 'gcc'
+	args += '-pthread'
+	link_args += '-pthread'
+endif
+
+if LTO_otp
+	if comp_id == 'gcc'
+		args += '-flto'
+		link_args += '-flto'
+	elif comp_id == 'llvm'
+		args += '-flto=thin'
+		link_args += '-flto=thin'
+	else
+		message('LTO don\'t work with DMD')
+	endif
+endif
+
 if betterC_opt
-	args += '-betterC'
-	link_args += '-betterC'
+	if comp_id == 'gcc'
+		args += ['-flto','-fno-druntime']
+		link_args += ['-flto','-fno-druntime']
+	else 
+		args += '-betterC'
+		link_args += '-betterC'
+	endif
 endif
 
 inc = include_directories('source/')
 tests_inc = include_directories('source/')
 
-ecs_lib = shared_library('ecs', src, include_directories : [tests_inc, inc], d_args: args, link_args: link_args)
+ecs_lib = library('ecs', src, include_directories : [tests_inc, inc], d_args: args, link_args: link_args)
 
 executable('tests', tests_src, include_directories : [tests_inc, inc], d_args: args, link_args: link_args, link_with: ecs_lib)
 
-
+if BuildDemos_opt
+	subdir('demos/utils')
+	subdir('demos')
+endif