[tests] skeleton for testing math lib with libtap

using [libtap](https://github.com/zorgnax/libtap) to create a [TAP](http://testanything.org) (TestAnythingProtocol) producer.
You can also run the test (if already compiled) with prove:
```
prove --exec '' tests/math/test_pprz_math.run
```

sw/airborne/math/Makefile

@@ -31,7 +31,7 @@ all:
 	@cat README
 
 shared_lib: $(OBJ)
-	$(CC) -shared -o $(BUILDDIR)/$(LIBNAME).so $(OBJ)
+	$(CC) -shared -o $(BUILDDIR)/$(LIBNAME).so $(OBJ) -lm
 
 install_shared_lib: shared_lib
 	test -d $(LIB_INSTALLDIR) || mkdir -p $(LIB_INSTALLDIR)

tests/Makefile

@@ -26,6 +26,7 @@ else
 endif
 
 test:
+	$(Q)make -C math test
 	$(Q)$(PERLENV) $(PERL) "-e" "$(RUNTESTS)"
 
 clean:

tests/math/.gitignore

@@ -0,0 +1 @@
+test_pprz_math.run

tests/math/Makefile

@@ -0,0 +1,64 @@
+# Copyright (C) 2014 Piotr Esden-Tempski
+#
+# This file is part of paparazzi.
+#
+# paparazzi is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2, or (at your option)
+# any later version.
+#
+# paparazzi is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with paparazzi; see the file COPYING.  If not, see
+# <http://www.gnu.org/licenses/>.
+
+# The default is to produce a quiet echo of compilation commands
+# Launch with "make Q=''" to get full echo
+
+# Make sure all our environment is set properly in case we run make not from toplevel director.
+Q ?= @
+
+PAPARAZZI_SRC ?= $(shell pwd)/../..
+ifeq ($(PAPARAZZI_HOME),)
+PAPARAZZI_HOME=$(PAPARAZZI_SRC)
+endif
+
+# export the PAPARAZZI environment to sub-make
+export PAPARAZZI_SRC
+export PAPARAZZI_HOME
+
+MATHSRC_PATH=$(PAPARAZZI_SRC)/sw/airborne/math
+MATHLIB_PATH=$(PAPARAZZI_SRC)/var/build/math
+
+#####################################################
+# If you add more test files you add their names here
+TESTS = test_pprz_math.run
+
+###################################################
+# You should not need to touch the rest of the file
+
+all: test
+
+math_shlib:
+	$(Q)cd $(MATHSRC_PATH); make shared_lib
+
+build_tests: math_shlib $(TESTS)
+
+test: build_tests
+	$(Q)for i in $(TESTS); do \
+	./$$i;	\
+	done
+
+%.run: %.c
+	$(CC) -L$(MATHLIB_PATH) -I$(PAPARAZZI_SRC)/sw/airborne -I$(PAPARAZZI_SRC)/sw/include tap.c $< -lpprzmath -o $@
+
+clean:
+	$(Q)rm -f $(MATHLIB_PATH)/*.o $(MATHLIB_PATH)/libpprzmath.so
+	$(Q)rm -f $(TESTS)
+
+
+.PHONY: math_shlib build_tests test clean all