UI: always use XFilterEvent on XEvent, so IM events work properly
UI: properly handle composed keys via utf8input in key events
UI: introduce EventData structure for CONTENT_DATA events
UI: handle XIM buffer overflow API conformant with Xutf8ResetIC
UI: guard event_context_ from XIM synthesized events
UI: fixup accidental XProperty items rename
RCORE: add utf8_is_locale_charset()
UI: handle XLookupString(3) returns in the locale charset
UI: fill in key symbol value for KEY_RELEASE events
Merge branch 'keyboard-input'

* keyboard-input:
  UI: fill in key symbol value for KEY_RELEASE events
  UI: handle XLookupString(3) returns in the locale charset
  RCORE: add utf8_is_locale_charset()
  UI: fixup accidental XProperty items rename
  UI: guard event_context_ from XIM synthesized events
  UI: handle XIM buffer overflow API conformant with Xutf8ResetIC
  UI: introduce EventData structure for CONTENT_DATA events
  UI: properly handle composed keys via utf8input in key events
  UI: always use XFilterEvent on XEvent, so IM events work properly