Build system and packaging (RPM support)

An update to the build system to properly support all commonly
used Makefile targets these include:

  make all        # Build everything
  make install    # Install everything
  make clean	  # Clean up build products
  make distclean  # Clean up everything
  make dist       # Create package tarball
  make srpm       # Create package source RPM
  make rpm        # Create package binary RPMs
  make tags       # Create ctags and etags for everything

Extra care was taken to ensure that the source RPMs are fully
rebuildable against Fedora/RHEL/Chaos kernels.  To build binary
RPMs from the source RPM for your system simply run:

  rpmbuild --rebuild spl-x.y.z-1.src.rpm

This will produce two binary RPMs with correct 'requires'
dependencies for your kernel.  One will contain all spl modules
and support utilities, the other is a devel package for compiling
additional kernel modules which are dependant on the spl.

  spl-x.y.z-1_<kernel version>.x86_64.rpm
  spl-devel-x.y.2-1_<kernel version>.x86_64.rpm

module/spl/spl-kmem.c

@@ -118,7 +118,6 @@ spl_kmem_availrmem(void)
 }
 EXPORT_SYMBOL(spl_kmem_availrmem);
 
-#if 0
 size_t
 vmem_size(vmem_t *vmp, int typemask)
 {
@@ -138,8 +137,6 @@ vmem_size(vmem_t *vmp, int typemask)
 	return size;
 }
 EXPORT_SYMBOL(vmem_size);
-#endif
-
 
 /*
  * Memory allocation interfaces and debugging for basic kmem_*