use std=c99

CMakeLists.txt

@@ -7,6 +7,8 @@ include_directories(ed25519-donna)
 set_source_files_properties(aeskey.c PROPERTIES
                             COMPILE_FLAGS -Wno-sequence-point)
 
+set(CMAKE_C_FLAGS "-std=c99")
+
 if(MSVC)
   set_source_files_properties(${SOURCES} PROPERTIES LANGUAGE CXX)
 endif(MSVC)
@@ -22,4 +24,4 @@ if (TREZOR_CRYPTO_TESTS)
     add_executable(test-openssl test-openssl.c)
     target_link_libraries(test-openssl TrezorCrypto check rt pthread m crypto)
     add_test(NAME trezor-crypto-openssl COMMAND test-openssl 100)
-endif()
+endif()

Makefile

@@ -3,6 +3,7 @@ CC        = gcc
 OPTFLAGS  = -O3 -g
 
 CFLAGS   += $(OPTFLAGS) \
+            -std=c99 \
             -W \
             -Wall \
             -Wextra \