Revert "no need to include library.o in the LAMMPS executable"

This reverts commit 4a3a6b44.
As it turns out, when using the LAMMPS python wrapper from inside
code using the PYTHON package, the library symbols *are* needed.
Thanks for Richard Berger (@rbberger) for pointing this out.

src/Makefile

@@ -17,12 +17,12 @@ SHLINK = liblammps.so
 OBJDIR =   Obj_$@
 OBJSHDIR = Obj_shared_$@
 
-SRC =	$(filter-out library.cpp,$(wildcard *.cpp))
-INC =	$(filter-out library.h,$(wildcard *.h))
+SRC =	$(wildcard *.cpp)
+INC =	$(wildcard *.h)
 OBJ = 	$(SRC:.cpp=.o)
 
-SRCLIB = $(filter-out main.cpp,$(SRC)) library.cpp
-OBJLIB = $(filter-out main.o,$(OBJ)) library.o
+SRCLIB = $(filter-out main.cpp,$(SRC))
+OBJLIB = $(filter-out main.o,$(OBJ))
 
 # Command-line options for mode: exe (default), shexe, lib, shlib
 
@@ -176,7 +176,7 @@ help:
 	  then cp Makefile.package.settings.empty Makefile.package.settings; fi
 	@cp Makefile.package Makefile.package.settings $(objdir)
 	@cd $(objdir); rm -f .depend; \
-	$(MAKE) $(MFLAGS) "SRC = $(SRC) library.cpp" "INC = $(INC) library.h" depend || :
+	$(MAKE) $(MFLAGS) "SRC = $(SRC)" "INC = $(INC)" depend || :
 ifeq ($(mode),exe)
 	@cd $(objdir); \
 	$(MAKE) $(MFLAGS) "OBJ = $(OBJ)" "INC = $(INC)" "SHFLAGS =" \