Compile error on ARMv7 platform

ghoscript builds all the sources (including brotli) using -Werror=declaration-after-statement which causes build failure of brotli/c/dec/decode.c when targeting ARMv7 platform.

That's because PreloadSymbol() starts with a statement followed by BROTLI_HC_MARK_TABLE_FOR_FAST_LOAD() macro which on ARMv7 expands to variable declaration.

See https://bugs.ghostscript.com/show_bug.cgi?id=708831 for details and a proposed patch.

Start with brotli/c/dec/decode.c, focusing on PreloadSymbol() and BROTLI_HC_MARK_TABLE_FOR_FAST_LOAD() as they expand for ARMv7. Reproduce the build with -Werror=declaration-after-statement and compare the behavior with the proposed patch in the linked report. Done means the ARMv7 build completes without this declaration-order error.

Written by the indexing model from the issue text.