John Denker:

Suggestion:  It might be helpful to promote each of
 the .c files to .cxx.

 Rationale:
 -- The configure/makefile system handles CFLAGS
    differently from CXXFLAGS.
 -- It is important for the *info programs to
    compiled and run in exactly the same environment
    as the main fgfs program.  Some users depend on
    compiler or linker flags such as rpath that
    strongly affect the results of the *info programs.
 -- There is no downside;  you code compiles just
    fine as-is under the c++ compiler.

timoore split the original patch so that alcinfo.cxx can be commited to
the ehofman/sound branch seperately.

tests/Makefile.am

@@ -8,10 +8,10 @@ else
 test_up_PLIB_LIBS = -lplibsg -lplibul
 endif
 
-est_epsilon_SOURCES = est-epsilon.c
+est_epsilon_SOURCES = est-epsilon.cxx
 est_epsilon_LDADD =  $(opengl_LIBS)
 
-gl_info_SOURCES = gl-info.c
+gl_info_SOURCES = gl-info.cxx
 gl_info_LDADD = $(opengl_LIBS)
 
 al_info_SOURCES = al-info.c