Revert "Remove support for 'texture expression' when loading textures"

This reverts commit 573041d6ee17152f40ecd92e8ee728833774b4f4.
Remove support for 'texture expression' when loading textures
Fix 4d3ed7a7db9dd34e97f80804d8edb7807f1c2e74

Regular images without extensions can be loaded again.
Fix CG_OnPlayerWeaponChange not being called when cycling through specs
Stop buffer overflows: CL_CheckForResend, Info_SetValueForKeyRocket, MSVC's _[v]snprintf
Merge pull request #348 from slipher/buffer_overflow

Stop buffer overflows: CL_CheckForResend, Info_SetValueForKeyRocket, MSV...
Move rocket_update from IN_Frame to CL_Frame
travis: mkdir: don't complain if the directory exists.
Fix png interlace handling warning
Use UTF-8 encoding directly for icon font characters instead of \u#### escape
sequence. Remove a couple of apparently unused alternate icons.
Merge pull request #350 from slipher/iconutf8

Use UTF-8 encoding directly for icon font characters
Merge branch 'master' of https://github.com/Unvanquished/Unvanquished into beacons