bugfix: overflow and some QA issues

bugfix: overflow and some QA issues

Fixes gentoo bug #338971

Patch from Kevin Pyle via Walther Maldonado (walther.md at gmail).
Modified patch to gkrellm-bgchanger-0.1.7 to fix overflow
and some QA issues

This patch addresses several issues with the upstream package:

- CC not set, so the simple name 'cc' was used.
  This disrupts cross-compilation.
- LDFLAGS misspelled as LFLAGS, so user LDFLAGS were not passed.
- CFLAGS had -O3 appended, overriding user's chosen -O level.
- Improper length passed to fgets, as reported in comment #0.

Bugzilla: http://bugs.gentoo.org/show_bug.cgi?id=338971
Reported-by: Walther Maldonado (walther.md at gmail.com)