1.2.0a

fix: Wild pointer crash in JPEGDEC MCU_SKIP handling (#1627)

Adds a PlatformIO pre-build script to patch JPEGDEC library. When
decoding progressive JPEGs with AC coefficients, MCU_SKIP (-8) causes
array index 0xFFFFF8, creating a wild pointer ~33MB past the sMCUs
array. The patch redirects pMCU to sMCUs[0] when MCU_SKIP is active,
preventing store-access faults while maintaining correct behavior for
JPEG_SCALE_EIGHTH decoding. Devices with larger framebuffers (like the
x3) (792×528 = 52,272 bytes vs 800×480 = 48,000 bytes) have less free
heap, shifting the allocation and changing where the wild pointer lands.

Commit 8628297 guarded the DC coefficient write (pMCU[0]) with if (iMCU
>= 0), which prevents crashes for progressive JPEGs whose first scan is
DC-only (iScanEnd == 0). However, if the first scan includes AC
coefficients (iScanEnd > 0), the AC decode loop still writes through the
wild pointer and crashes.