test : build fix when --enable-pdf=no

Though --enable-pdf=yes by default, when --enable-pdf=no, the cairo build
fails due to unavailability of cairo-pdf.h and related cairo pdf's apis.
The current changes fixes this issue by conditionally checking if PDF
surface is enabled or not.

Signed-off-by: Ravi Nanjundappa <nravi.n@samsung.com>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>
Tested-by: Bryce Harrington <bryce@osg.samsung.com>
V5: Use NEAREST filter when possible

(changed to use determinant funciton and remove debug printf)

Modifies _cairo_matrix_has_unity_scale to return true for 90 degree rotations
by allowing error caused by inaccuracy in trig functions.

This fails after 14 additions of M_PI_2 to itself as a float argument to
cairo_rotate, but the failure is in the detection of the integer translate,
not in the trig components. I believe this is due to the matrix inversion,
which may need similar rounding.

Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>
test: Selective execution of Cairo tests based on FORMAT option

Added a new command line option FORMAT which can take rgb and/or rgba
values which enables the execution of tests only for the given FORMAT
For ex:
(1). CAIRO_TESTS="zero-alpha" make test TARGETS=ps2,image FORMAT=rgba,rgb
This command runs the zero-alpha test for both ps2 and image backends
with argb32 and rgb24 content formats.
(2). CAIRO_TESTS="zero-alpha" make test TARGETS=ps2,image FORMAT=rgba
This command runs the zero-alpha test for both ps2 and image backends
with argb32 content format and so on.

Signed-off-by: Ravi Nanjundappa <nravi.n@samsung.com>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
test: improve selective execution of Cairo tests based on FORMAT option

This patch improves the patch "test: Selective execution of Cairo tests based on FORMAT option"
by extending the usage of FORMAT option even in the case of user not
providing TARGETS= option

For ex:
(1). CAIRO_TESTS="zero-alpha" make test FORMAT=rgba
This command runs the zero-alpha test for all the backends with
argb32 content format and so on.
(2). CAIRO_TESTS="zero-alpha" make test FORMAT=rgba,rgb
This command runs the zero-alpha test for all the backends with
argb32 and rgb24 content formats.

Signed-off-by: Ravi Nanjundappa <nravi.n@samsung.com>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
README : Update README file related to usage of FORMAT make variable

Reformatted the README file to simplify the sentences.

Signed-off-by: Ravi Nanjundappa <nravi.n@samsung.com>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>