warnings: fix warnings when everything possible is turned on

warnings: fix warnings when everything possible is turned on

Tested with gcc (GCC) 6.2.1 20160830 and following options

CFLAGS="-O -fPIC -D_FORTIFY_SOURCE -W -Wabi -DANOTHER_BRICK_IN_THE -Wall
-Wattributes -Wbad-function-cast -Wbuiltin-macro-redefined -Wcast-align
-Wchar-subscripts -Wcoverage-mismatch -Wcpp -Wdeclaration-after-statement
-Wdeprecated -Wdeprecated-declarations -Wdisabled-optimization
-Wdiv-by-zero -Wendif-labels -Wextra -Wfloat-equal -Wformat-contains-nul
-Wformat-extra-args -Wformat-nonliteral -Wformat-security -Wformat-y2k
-Wformat-zero-length -Wformat=2 -Winit-self -Winvalid-pch -Wlogical-op
-Wmissing-declarations -Wmissing-include-dirs -Wmissing-noreturn
-Wmissing-prototypes -Wmultichar -Wnested-externs -Wno-format-nonliteral
-Wno-inline -Wno-logical-op -Wno-long-long -Wno-missing-field-initializers
-Wno-overlength-strings -Wno-sign-compare -Wno-unused-parameter
-Wno-unused-result -Wnormalized=nfc -Wold-style-definition -Woverflow
-Woverlength-strings -Wpacked -Wpacked-bitfield-compat -Wpointer-arith
-Wpointer-to-int-cast -Wpragmas -Wredundant-decls -Wshadow -Wsign-compare
-Wstrict-aliasing -Wstrict-aliasing=2 -Wstrict-prototypes
-Wsuggest-attribute=noreturn -Wsync-nand -Wtrampolines -Wtype-limits
-Wundef -Wuninitialized -Wunknown-pragmas -Wunused -Wunused-local-typedefs
-Wvla -Wvolatile-register-var -Wwrite-strings -fdata-sections
-fdiagnostics-show-option -ffunction-sections -fno-common -funit-at-a-time
-fvisibility=hidden -pipe" ./configure && make