test : Maintain consistency in the usage of xcalloc

xcalloc is a wrapper for calloc. If it can't allocate memory then it
terminates the program. The current changes replace the usages of calloc
by xcalloc in tests.

Signed-off-by: Ravi Nanjundappa <nravi.n@samsung.com>
vg: Use EGL_NONE and GLX_NONE in place of None

Use EGL_NONE in EGL section and GLX_NONE in GLX section
instead of None in cairo-boilerplate-vg.c

Signed-off-by: Ravi Nanjundappa <nravi.n@samsung.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=55805