Update Makefile.in: harden binaries with RELRO mitigations

[kbipinkumar]

first of all i would like to thank you for adding support for adding support for staged install as suggested in issue #61.

binaries produced by current Makefile lack common security mitigation such as RELRO as recommended by major linux distribution including debian

spaln W: ELF file ('usr/bin/makdbs') lacks FULL RELRO, check LDFLAGS.
spaln W: ELF file ('usr/bin/makmdm') lacks FULL RELRO, check LDFLAGS.
spaln W: ELF file ('usr/bin/sortgrcd') lacks FULL RELRO, check LDFLAGS.
spaln W: ELF file ('usr/bin/spaln') lacks FULL RELRO, check LDFLAGS.

currently distros are patching the Makefile.in with requisite flags for hardening the spaln binaries. this pull request, based on debian-med project's patches, adds the aforementioned flags to `Makefile.in' so the packagers can pass appropriate hardening option during build time.