make: comprehensive list of the boards' filesizes
make: add maketarget to to show the biggest obj files
make: show diffence in buildsizes for two folders
drivers: fix includes in rtc.h for MSP430

The comment and the actual guard in `rtc.h` did not match.
If (as in "implication") the MCU is an MSP, then `sys/time.h` must be
included, to have `time_t`, `struct timeval`, …

Including the header file in any case should be safe, so I dropped the
guard altogether.
Merge pull request #1033 from Kijewski/buildsizes

make: comprehensive list of the boards' filesizes
add pthread condition variable implementation
Merge pull request #771 from BytesGalore/add_CV_module

pthread: Add condition variable module
added else branch in `pthread_exit()` to avoid calling explicit `return;`
however, this won't help to completely eliminate the warning on returning from a `noreturn` function
Merge pull request #1076 from BytesGalore/remove_return_from_noreturn_function

sys:posix:pthread removed explicit `return;` from `pthread_exit()`
Merge pull request #1073 from Kijewski/rtc-sys_time

drivers: fix includes in rtc.h for MSP430