This should fix the bug, probably introduced with the per-directory
performance enhancements, that after a change to an IDL file 2 builds
are required to rebuild everything.

See also: 5513e24e

Part XXXVIII
Modules
svx

Reverted
80f60ef540528ec5304b9fb9624a7ff1b077f108
cf1f87948bcf9b8edf8487fa7938a928cfed8f2f
as also MinGW bails out. Don't add yet more quirks, keep in mind the faulty
behavior and hope for the best until solved.

Modifies the workaround of 6ecf6ea7

Zooming does now base on a geometric progression instead of an
arithmetic one.
Since the zoom factor is not only used in Draw but for all other
applications 1.2 seems like a good choice.

At least with gcc 4.6.2 the situation was that if /usr/include was missing
from the -I... includes, header files were pulled from /usr/include/
instead of solver/$INPATH/inc/external/

This clearly makes a difference for not --with-system-... libs where the
internal version is to be used.