eci.c: replace libiconv-adapted code with own implementations so

as to fully comply with BSD license (for why Library GPL 2+ not
  compatible see https://opensource.stackexchange.com/a/6701),
  ~3% slower (maybe), +~6K extra in data
  (gb18030.c, gb2313.c & sjis.c removed, mapping .TXT files moved
  to backend/tools/data & extra ones added, 2 new PHP generators)
GUI: CODE39/EXCODE39: show/hide HIBC check digit option in addition
  to enable/disable (less confusing)
CLI: batch: pedantic check for EOF using intChar in newline fgetc()
  loop
test_args.c: don't use WIFEXITED(), WEXITSTATUS() on Windows
manual: lessen some copy/paste verbiage by referring back, other
  small tweaks/typos

backend_tcl/configure

@@ -5581,8 +5581,6 @@ done
 	../backend/dotcode.c
 	../backend/eci.c
 	../backend/emf.c
-	../backend/gb18030.c
-	../backend/gb2312.c
 	../backend/general_field.c
 	../backend/gif.c
 	../backend/gridmtx.c
@@ -5605,7 +5603,6 @@ done
 	../backend/raster.c
 	../backend/reedsol.c
 	../backend/rss.c
-	../backend/sjis.c
 	../backend/svg.c
 	../backend/telepen.c
 	../backend/tif.c