Drop orphaned utf8_strlen()
utf8_strncpy → g_utf8_strncpy
Drop orphaned {u,cu}_strstartmatch()
Drop orphaned uc_strnmatch
c_strlen → strlen
Drop orphaned u_copynallocm
Drop orphaned utf8_{db,ib}
Drop orphaned uc_strncat()
Drop MEMORY_MASK thing

Never defined, very likely for manual memory debugging.
Drop orphaned utf8_2_latin1_copy()
Eliminate utf8_truncatevalid() usage

It is a direct consequence of evilness of fixed char array; use
glib GString in kerning table popup to avoid char array.
utf8_valid → g_utf8_validate