use correct $TERM env. var. under Linux

[Konfekt]

because $TERM_PROGRAM is only used by Mac OS

[cgundogan]

+1 for this change

[Konfekt]

Thanks for the support. How about @altercation should at some point deferring privileges to chosen members to resolve these semantic issues?

[antoineco]

Stumbled upon this while trying to figure out why italics were enabled in GVim but not terminal Vim.

$TERM is typically set to either xterm or rxvt, which is too vague to guarantee that italics is supported by the emulator or even enabled.

#120 is the way to go instead.