Eliminate addcarryx/subborrowx wrappers in Go

This is a partial fix for item 1 of
mit-plv#949 (comment) also
mentioned at golang/go#40171 (comment)

Unfortunately, we still cast the arguments to uint1 because we don't
have enough information in the right places to relax the casts.  We
really want a fused absint/rewriting pass, where we get access to true
bounds information rather than just casts.

Makefile

@@ -272,7 +272,7 @@ BEDROCK2_EXTRA_CFLAGS := -Wno-error=unused-but-set-variable
 
 RUST_EXTRA_ARGS := --inline
 
-GO_EXTRA_ARGS_ALL := --cmovznz-by-mul --internal-static --package-case flatcase --public-function-case UpperCamelCase --private-function-case camelCase --public-type-case UpperCamelCase --private-type-case camelCase --no-prefix-fiat --doc-newline-in-typedef-bounds --doc-prepend-header 'Code generated by Fiat Cryptography. DO NOT EDIT.' --doc-text-before-function-name '' --doc-text-before-type-name ''
+GO_EXTRA_ARGS_ALL := --relax-primitive-carry-to-bitwidth 32,64 --cmovznz-by-mul --internal-static --package-case flatcase --public-function-case UpperCamelCase --private-function-case camelCase --public-type-case UpperCamelCase --private-type-case camelCase --no-prefix-fiat --doc-newline-in-typedef-bounds --doc-prepend-header 'Code generated by Fiat Cryptography. DO NOT EDIT.' --doc-text-before-function-name '' --doc-text-before-type-name ''
 GO_EXTRA_ARGS_64  := --no-wide-int $(GO_EXTRA_ARGS_ALL)
 GO_EXTRA_ARGS_32  := $(GO_EXTRA_ARGS_ALL)
 

_CoqProject.in

@@ -201,6 +201,7 @@ src/Rewriter/Passes/MulSplit.v
 src/Rewriter/Passes/MultiRetSplit.v
 src/Rewriter/Passes/NBE.v
 src/Rewriter/Passes/NoSelect.v
+src/Rewriter/Passes/RelaxBitwidthAdcSbb.v
 src/Rewriter/Passes/StripLiteralCasts.v
 src/Rewriter/Passes/Test.v
 src/Rewriter/Passes/ToFancy.v