loaders: Fix stubs.

Fix GP_ReadJPG() and GP_ReadTIFF() stubs.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
configure: Make use of args.

* Make use of args, so that ./configure CC=gcc works in
  addition to CC=gcc ./configure and ./configure --CC=gcc

* Complain loudly on invalid arguments, previously
  everything that wasn't option (haven't started with '-'
  was silently ignored).

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
loaders: TIFF: Change tmsize_t to tsize_t

Fixes build with tiff 3.9.6

Signed-off-by: Cyril Hrubis <metan@ucw.cz>