[Piglit] [PATCHv2 00/10] add infrastructure for GLES1 tests

[Chia-I Wu]

Changes since v1 are

 - change how switch cases are guarded in piglit_get_gl_error_name
 - rename piglit-util-gles2.c to piglit-util-gles.c, and let GLES1 and
   GLES2 share it
 - hide enum naming differences in gl_wrap.h
   (e.g. define GL_TEXTURE_CUBE_MAP_POSITIVE_X to
    GL_TEXTURE_CUBE_MAP_POSITIVE_X_OES for GLES1)
 - call piglit_report_result(PIGLIT_SKIP) when piglit_require_GLSL or
   other shader related helpers are called in piglitutil_gles1