Misc. minor fixes.

[AliceLR]

• Disable Vorbis ogg linking test for scripts/deps. Fixes libvorbis compilation issues for PLATFORM=linux-msan found in an Ubuntu chroot.
• Regression tests were missing ZLIB_CFLAGS (found in Ubuntu chroot MSan builds).
• SDL icon surfaces could be leaked when failing to set the surface (occurs with the SDL dummy renderer).
• Fixed case where intake Ctrl+Left could cause out-of-bounds reads.
• Added guards for get_string calls in expr.c.
• Copyright for original tr_msg in expr.c.