Install header files and static library, add missing header.

diff --git a/build/general/Makefile.inc b/build/general/Makefile.inc
index 77d4b65..e887471 100644
--- a/build/general/Makefile.inc
+++ b/build/general/Makefile.inc
@@ -4,6 +4,7 @@ CXX	?= g++
 CC	?= gcc
 AR	?= ar
 RANLIB	?= ranlib
+INSTALL	?= install -p
 
 CFLAGS	:= $(CFLAGS) -I.
 CXXFLAGS	:= $(CXXFLAGS) -I.
@@ -42,6 +43,7 @@ HEADERS := base/Pitch.h \
            maths/KLDivergence.h \
            maths/MathAliases.h \
            maths/MathUtilities.h \
+           maths/nan-inf.h \
            maths/Polyfit.h \
            maths/pca/pca.h \
            thread/AsynchronousTask.h \
@@ -89,6 +91,12 @@ $(LIBRARY):	$(OBJECTS)
 		$(AR) cr $@ $^
 		$(RANLIB) $@
 
+install:
+		$(INSTALL) -D -m 0644 $(LIBRARY) $(DESTDIR)$(LIBDIR)/$(LIBRARY)
+		for h in $(HEADERS); do \
+			$(INSTALL) -D -m 0644 $$h $(DESTDIR)$(PREFIX)/include/qm-dsp/$$h; \
+		done
+
 clean:		
 		rm $(OBJECTS)