Utilize the new "all" ARCHITECTURES keyword in most recipes. (#6189)

x86_64 is used as a baseline: the "x86_64" entry, whatever status it has,
is transformed into "all", and then the other entries in ARCHITECTURES
either dropped or rearranged appropriately.

games-simulation/corsix_th/corsix_th-0.62.recipe

@@ -18,7 +18,7 @@ SOURCE_DIR="CorsixTH-$portVersion"
 PATCHES="corsix_th-$portVersion.patchset"
 ADDITIONAL_FILES="corsix_th.rdef.in"
 
-ARCHITECTURES="!x86_gcc2 x86 x86_64"
+ARCHITECTURES="all !x86_gcc2"
 if [ "$targetArchitecture" = x86_gcc2 ]; then
 SECONDARY_ARCHITECTURES="x86"
 fi

games-simulation/lincity_ng/lincity_ng-2.9~git.recipe

@@ -17,7 +17,7 @@ SOURCE_FILENAME="lincity_ng-$srcGitRev.tar.gz"
 SOURCE_DIR="lincity-ng-$srcGitRev"
 PATCHES="lincity_ng-$portVersion.patchset"
 
-ARCHITECTURES="!x86_gcc2 x86 x86_64"
+ARCHITECTURES="all !x86_gcc2"
 SECONDARY_ARCHITECTURES="x86"
 
 PROVIDES="

games-simulation/openttd/openttd-1.7.1.recipe

@@ -11,7 +11,7 @@ SOURCE_URI="http://binaries.openttd.org/releases/$portVersion/openttd-$portVersi
 CHECKSUM_SHA256="61190952a98d494d3fd62e395dd6c359609914d0ba8fe80eaeb585b7d62a1b36"
 ADDITIONAL_FILES="openttd.rdef"
 
-ARCHITECTURES="!x86_gcc2 x86 x86_64"
+ARCHITECTURES="all !x86_gcc2"
 SECONDARY_ARCHITECTURES="x86"
 
 PROVIDES="

games-simulation/simutrans/simutrans-122.0.recipe

@@ -18,7 +18,7 @@ SOURCE_FILENAME="simutrans-$GitRevision.tar.gz"
 SOURCE_DIR="simutrans-$GitRevision"
 PATCHES="simutrans-$portVersion.patchset"
 
-ARCHITECTURES="!x86_gcc2 x86_64"
+ARCHITECTURES="all !x86_gcc2"
 SECONDARY_ARCHITECTURES="?x86"
 
 PROVIDES="

games-simulation/thepowdertoy/thepowdertoy-91.5.330.recipe

@@ -15,7 +15,7 @@ CHECKSUM_SHA256="9a7de557e771f88e823d06cc21d16f1fbbca930ce751720bc9035d00073d663
 SOURCE_DIR="The-Powder-Toy-$portVersion"
 PATCHES="thepowdertoy-$portVersion.patchset"
 
-ARCHITECTURES="x86_gcc2 x86 x86_64"
+ARCHITECTURES="all"
 
 PROVIDES="
 	thepowdertoy = $portVersion