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 )

so the question is: when ARDUINO_PLATFORM_LIB_PATH is not used (on 1.0.x) should it be printed (as empty) or not printed at all...
On 1.0.x variable will not be used even if set explicit, so maybe not printing is better solution, as you proposed. And then maybe also do not print variable value explicit set by user when using arduino 1.0.x (as not used at all)?
I am open for suggestions what you think is more consistent with "general spirit" of the project