Typedefs starting with `t' in linuxdoom

• texpatch_t src/r_data.c:107
• texture_t src/r_data.c:125
• thinkerclass_t src/p_saveg.c:225
• thinker_t src/d_think.h:70
• think_t src/d_think.h:60
• tSigSet src/i_sound.c:902