VirtGL: Fix warnings about g_malloc, g_free, g_realloc.

VirtGL: Fix warnings about g_malloc, g_free, g_realloc.

There are multiple definitions of these funcs, it induces warnings.
In file included from opengl_exec.c:64:0:
range_alloc.h:29:7: attention : redundant redeclaration of ‘g_malloc’ [-Wredundant-decls]
/usr/include/glib-2.0/glib/gmem.h:72:10: note: previous declaration of ‘g_malloc’ was here
tizen/src/hw/range_alloc.h:30:7: attention : redundant redeclaration of ‘g_realloc’ [-Wredundant-decls]
/usr/include/glib-2.0/glib/gmem.h:74:10: note: previous declaration of ‘g_realloc’ was here
tizen/src/hw/range_alloc.h:31:6: attention : redundant redeclaration of ‘g_free’ [-Wredundant-decls]
/usr/include/glib-2.0/glib/gmem.h:70:7: note: previous declaration of ‘g_free’ was here
tizen/src/hw/opengl_exec.c:114:7: attention : redundant redeclaration of ‘g_malloc’ [-Wredundant-decls]
tizen/src/hw/range_alloc.h:29:7: note: previous declaration of ‘g_malloc’ was here
tizen/src/hw/opengl_exec.c:115:7: attention : redundant redeclaration of ‘g_realloc’ [-Wredundant-decls]
tizen/src/hw/range_alloc.h:30:7: note: previous declaration of ‘g_realloc’ was here
tizen/src/hw/opengl_exec.c:116:6: attention : redundant redeclaration of ‘g_free’ [-Wredundant-decls]
tizen/src/hw/range_alloc.h:31:6: note: previous declaration of ‘g_free’ was here

Change-Id: I9e2557851216a44f970e83dd8ed16cb0e5e5f0d6