Improve logic to allow extending the test script
Add configuration time detection of GPG
Turn INCLUDE into an canonical file group
Fix the definition of our symbolic link tool
Rewrite the project module
Recursively create object directories

The bps.objdir.mk module always create an obj target, which prevents
bps.subdir.mk to delegating this to subdirectories. To keep bps.subdir.mk
as general as possible, we add the required dependance in bps.project.mk.
Write a moderately complex C project
Rename macro to match dominant convention
Improve the detection of manual pages

The exists predicate used to detect the manual pages will not consider
specialised versions of .PATH as .PATH.3, and so on. Therefore we
add ${DIRS} to .PATH.
Use the appropriate name for the debugging information target
Prevent the inflation of product lists
Rework the logic for suffixes and lookup paths

The definition of lookup paths cannot rely on the DIRS variable,
which contains only directories in the source tree, while we need
to find some files in the object tree.  They therefore need to be
initialised by the “module” module, as it examines the list of
products in the software package.

The list of suffixes is moved to the general initialisation file,
as it is a characteristic of the framework and must have been processed
before initialising lookup paths.
Link dependant libraries with the program

Note that libraries must appear on the command line *after* the objects
referencing their symbols, therefore the dependancy order is very important.
Prefer the use of specialised directory lookup over general one
Build a complex C program with multiple settings
Do not use all of CFLAGS

It is wrong to pass all of CFLAGS to the mkdep program, as it
only understands the -I option for include directories.
Worse, the -p flag used to add profiling information to compiled objects
has a completely different meaning for mkdep, which it instructs
to build dependencies for programs rather than for objects.
Use the GNU profiler tool
Promote warning about UFOs passed to the links to an error
Build a program for multiple architectures

Closes #131
Merge branch 'topic/test-complex-c-project'