Build a simple static library

Closes #124
Move langc library test to the test source tree

On the way, we had support for the DIRS variable in bps.man.mk. It allows
to put the manual pages in a different directory than where the Makefile is.
Build a simple static library with debugging or profile
Merge branch 'topic/test-simple-c-library'

Closes #124, #125, #126.