Arduino 1.5.x libs - handle new library layout (issue #275) and hardware/vendor specific libs (issue #276)  

My 3 cents for full arduino 1.5.x support (issue #45):
- (issue #276) when arduino 1.5.x is detected, additional path is searched for hardware/vendor specific libraries (aka $(ARDUINO_PLATFORM_LIB_PATH) ) - defaults to $(ARDUINO_DIR)/hardware/arduine/$(ARCHITECTURE)

- (issue #275) support for new arduino library layout, as specified in https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5:-Library-specification .
New layout is assumed when there are library.properties file and src subdirectory in library directory.
In new layout mode src subdirectory is searched recursively for library sources (using rwildcard)

- additional small thing allowing compiling 1.5.x libraries - define ARDUINO_ARCH_XXX when compiling (needed for system libraries in 1.5.x)

(Tested in arduino 1.0.5 and current ide-1.5.x branch )

shouldn't $(call....) be inside the endif, otherwise if we've not set it and we're no on 1.5 we get:

```- [COMPUTED]           ARDUINO_PLATFORM_LIB_PATH =  (from ARDUINO_DIR)```

and the variable is not used anyway.