The rendering code (draw.c) applies cairo_rotate() before
cairo_translate() for CIRCLE, LINE21, and LINE22 macro primitives,
meaning the rotation parameter already rotates the center coordinates
as part of the Cairo transformation.

The image copy/transform code (gerb_image.c) was updating the rotation
parameter AND calling gerbv_rotate_coord() on the center coordinates.
When the exported file was re-loaded, the center was rotated twice:
once by the pre-rotated coordinates, and again by cairo_rotate().

Remove the redundant gerbv_rotate_coord() calls for CIRCLE and
LINE21/LINE22, matching the pattern already used by LINE20, POLYGON,
MOIRE, and THERMAL — all of which correctly rely on the rotation
parameter alone.

Fixes gerbv#233