Fix int overflow in PCX image buffer sizing, now throws AllocationRequestException

[alhudz]

Reading the PCX decoder I noticed getBufferedImage sizes the pixel buffer with int multiplies of xSize/ySize, which both come from uint16 header fields and can reach 65536. For 24/32-bit and 8-bit/3-plane images rowLength * ySize, xSize * ySize and ySize * bytesPerImageRow overflow int and wrap small, so the value slips past the Allocator 1 GB guard and an undersized buffer feeds an out-of-bounds arraycopy. Computing in long lets the existing Allocator.byteArray(long) overload reject the real size instead.

[garydgregory]

@alhudz
There is no test for this PR.

[alhudz]

Added one in PcxImageParserTest. It feeds a crafted 128-byte header with bitsPerPixel=24, nPlanes=1 and xMax=yMax=65535 (so xSize=ySize=65536), which makes rowLength * ySize (196608 * 65536) overflow int and wrap small.

• expected: AllocationRequestException from the 1 GB Allocator guard
• before the fix: the wrapped size allocates an undersized buffer and you get an ArrayIndexOutOfBoundsException from the arraycopy
• after: the size is computed in long so the guard sees the real ~12 GB request and rejects it

Verified the test fails on master and passes with the fix.

[garydgregory]

@alhudz
As stated in the PR template, run 'mvn' by itself, and fix issues before you push.

[alhudz]

Good catch. Running mvn flagged a checkstyle LineLength violation in the test javadoc (line was 161 chars, limit 160). I've wrapped it and the default goal is green now: clean verify apache-rat:check checkstyle:check spotbugs:check pmd:check all pass with the new test included.