in calculations when gmtoff was not initialized before first use

Mimic what OAI's asnfix.c of generate_asn1 script does.

Mimic what OAI's asnfix.c of generate_asn1 script does.

asn1c_save.c:238:5: error: this ‘for’ clause does not guard... [-Werror=misleading-indentation]
     for(int i = 0; i < argc; i++)
     ^~~
asn1c_save.c:240:2: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the ‘for’
  safe_fprintf(mkf, "\n\n");
  ^~~~~~~~~~~~

../skeletons/INTEGER.c:510:60: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
             if(specs && specs->field_unsigned && dec_value <= ULONG_MAX) {

This fixes the following undefined behaviour

converter-example.c:721:13: runtime error: null pointer passed as argument 2, which is declared to never be null
/usr/include/string.h:44:28: note: nonnull attribute specified here

Previously some uper_* function were called

When there were no any padding bits the uper and aper decoders where
trying to read some which results in read past the buffer end.

See https://github.com/mouse07410/asn1c/issues/33#issuecomment-374625610

ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000000315 at pc 0x000102ce9c15 bp 0x7fff5d20a8d0 sp 0x7fff5d20a8c8
READ of size 1 at 0x602000000315 thread T0
    #0 0x102ce9c14 in asn_get_few_bits asn_bit_data.c:132
    #1 0x102d878fd in aper_open_type_get_simple per_opentype.c:455
    #2 0x102d85dcc in aper_open_type_get per_opentype.c:514

This fixes the following undefined behaviour

converter-example.c:721:13: runtime error: null pointer passed as argument 2, which is declared to never be null
/usr/include/string.h:44:28: note: nonnull attribute specified here

Previously some uper_* function were called

When there were no any padding bits the uper and aper decoders where
trying to read some which results in read past the buffer end.

See https://github.com/mouse07410/asn1c/issues/33#issuecomment-374625610

ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000000315 at pc 0x000102ce9c15 bp 0x7fff5d20a8d0 sp 0x7fff5d20a8c8
READ of size 1 at 0x602000000315 thread T0
    #0 0x102ce9c14 in asn_get_few_bits asn_bit_data.c:132
    #1 0x102d878fd in aper_open_type_get_simple per_opentype.c:455
    #2 0x102d85dcc in aper_open_type_get per_opentype.c:514

This reverts commit 4a668cbf.

This reverts commit 8946c21d.

This reverts commit 87e34efe.

This reverts commit fb4d5af4.

This reverts commit 012a9937.

deficiencies of vlm/#260).

by casting dec_value to unsigned (uintmax_t)