perf: Guarantee path width is non-negative

This quells the following warning:

  perf/micro/hatching.c:39:5: warning: cannot optimize loop, the
  loop counter may overflow

Width and height aren't going to be negative so enforce it so that the
compiler can do whatever optimization it wants to do.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
test: Quell warning for inclusion of old rsvg header files

This silences a warning due to header file deprecated as of libsrvg
2.36.2.  Tested and verified this hackaround on librsvg 2.36.4 and
2.36.1.  No need to change version dependencies.

  In file included from test/any2ppm.c:73:0:
  /usr/include/librsvg-2.0/librsvg/rsvg-cairo.h:27:2: warning:
  #warning "Including <librsvg/rsvg-cairo.h> directly is deprecated."

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
test: Quell warning for deprecated g_type_init()

The g_type_init() routine was deprecated in glib 2.34.  Tested and
verified this conditionalization on glib 2.32 and 2.36.  No need to
change version dependencies.

  test/any2ppm.c:864:5: warning: ‘g_type_init’ is deprecated
  (declared at /usr/include/glib-2.0/gobject/gtype.h:669)

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
xml: Drop unused variable

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
xml: constify source objects for emit routines

This quells the following warnings:

  src/cairo-xml-surface.c:576:5: warning: passing argument 2 of
  ‘_cairo_xml_surface_emit_clip_boxes’ discards ‘const’ qualifier from
  pointer target type
  src/cairo-xml-surface.c:462:1: note: expected ‘struct cairo_clip_t
  *’ but argument is of type ‘const struct cairo_clip_t *’

Most of the cairo_xml*emit* routines const their source objects;
these should follow suit.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
mesh: Avoid theoretical infinite loops

This quells this warning:

  src/cairo-mesh-pattern-rasterizer.c:731:5: warning: cannot
  optimize possibly infinite loops

I guess the compiler's complaining because if vsteps were negative or
equal to UINT_MAX the loop could cycle infinitely.  Silly compiler.

Fix as suggested by Chris Wilson <chris@chris-wilson.co.uk>
gl: Handle PIXMAN_a8r8g8b8_sRGB format in switch

Fixes the following compiler warning:

  cairo-gl-surface.c:182:5: warning: enumeration value
  ‘PIXMAN_a8r8g8b8_sRGB’ not handled in switch

Same fix as done for image in 1d0055078.

Chris Wilson <chris@chris-wilson.co.uk>