mesa: Include stdint.h in mtypes.h for uint32_t symbol.

This patch fixes the MSVC build error introduced with commit
b2e327e08f8519da131dd382adcc99240d433404.

api_arrayelt.c
src\mesa\main/mtypes.h(1809) : error C2061: syntax error : identifier 'uint32_t'
src\mesa\main/mtypes.h(1810) : error C2059: syntax error : '}'
src\mesa\main/mtypes.h(1825) : error C2079: 'Minimum' uses undefined union 'gl_perf_monitor_counter_value'
src\mesa\main/mtypes.h(1828) : error C2079: 'Maximum' uses undefined union 'gl_perf_monitor_counter_value'

Signed-off-by: Vinson Lee <vlee@freedesktop.org>