Project is not compatible with PlatformIo

[williamesp2015]

Hi. this is great websocket project for ESP32 because there is no source for it. Unfortunately I couldn't import to PlatformIo using ESP32.

[sloanyyc]

base64 function don't work with 32bit process.
modify lib/aw-base64.h below 32->23. make it compatible with 32bit process.
*buf++ = (((n - 0 - i) >> 31) & '=') |
(((n - 0 - i) >> 31) & t[x >> 1 * 6 & 0x3f]);
*buf++ = (((n - 1 - i) >> 31) & '=') |
(((n - 1 - i) >> 31) & t[x >> 0 * 6 & 0x3f]);